A crossword setter has to employ little tricks to get the job done properly. It’s easy to almost get it right, imply something or be in the neighourhood, but it takes effort to nail it beyond reproach. I know instinctively, for instance, when a clue doesn’t quite work for me, and I say “for me”, because I don’t think all solvers particularly care about being perfect, and will give a setter latitude without realising that they are doing so.
10-down in this crossword is Available money a unit’s members count up primarily (13) and is made up of “Available money (FUND) a (A) unit’s members (MEN) count up (TALLY) = primarily”. Can you see the trick used here? On the surface it looks like a straightforward charade, but there’s a snag in the construction: how do you place “A”, the indefinite article that precedes a singular word, next to “MEN” which is plural? If you simply substitute another word for “MEN” you will get a mismatch, so a little creative thinking is required. Here I’ve butted and singular term (UNIT’S) with a plural one (MEMBERS) that leads to a plural answer (MEN), thus keeping the grammar intact. This kind of thing can also cause problems joining definition and wordplay, but some rearranging or neat language can overcome just about anything our English language puts in the way.
The Stickler
I missed the singular/plural issue, but agree totally with the explanation which demonstrates that the clue is technically correct. One of the tips I was given early in my career, was to ignore punctuation. Obviously the discerning solver will need to evaluate the punctuation in the same way he evaluates the rest of the clue.