A bit of profit, and not for the first time (5)
I believe the answer is:
again
'not for the first time' is the definition.
(I've seen this before)
'a bit of profit' is the wordplay.
'bit of profit' becomes 'gain' (I can't explain this - if you can you should give a lot more credence to this answer).
'a'+'gain'='AGAIN'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for again that I've seen before include "Predictably perhaps" , "Here we go ___" , "Furthermore" , "10 10 [AGAIN" , "'Another time, once more (5)'" .)