So it sounds like they're in favour! (9)
I believe the answer is:
therefore
'so' is the definition.
(I know that so can be written as therefore)
'it sounds like they're in favour' is the wordplay.
I cannot really see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
'in favour' could be 'for' (as in being for a particular cause) and 'for' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for therefore that I've seen before include "It follows" , "as result" , "Consequently - for that reason" , "has a triangular formation in maths?" , "In consequence" .)