Profit in a way when in opposition (7)
I believe the answer is:
against
'in opposition' is the definition.
(I've seen this before)
'profit in a way when' is the wordplay.
'profit' becomes 'gain' (synonyms).
'in' indicates putting letters inside.
'a way when' becomes 'ast' (I can't justify this - if you can you should believe this answer much more).
'gain' put inside 'ast' is 'AGAINST'.
Can you help me to learn more?
(Other definitions for against that I've seen before include "Opposed" , "antagonistic" , "on the other side" , "Opposing" , "Disapproving of" .)