Short of money, firm finished (4,2)
I believe the answer is:
hard up
'short of money' is the definition.
(I've seen this before)
'firm finished' is the wordplay.
'firm' becomes 'hard' (both can mean durable or strong).
'finished' becomes 'up' (eg 'time's up' means the time is finished).
'hard'+'up'='HARD-UP'
(Other definitions for hard up that I've seen before include "Being without cash" , "Short of cash" , "Struggling with budget" , "Having little money, almost skint" , "Strapped for cash, it's tough" .)