Not in favour of a profit split after vacation (7)
I believe the answer is:
against
'not in favour of' is the definition.
(I've seen this before)
'a profit split after vacation' is the wordplay.
'profit' becomes 'gain' (synonyms).
'after vacation' means to remove the middle letters (the inside letters must vacate).
'split' with its centre removed is 'st'.
'a'+'gain'+'st'='AGAINST'
(Other definitions for against that I've seen before include "Facing" , "Opposed" , "Placed in direct contact with" , "Not in favour of" , "In opposition to" .)