Silly fellow ignoring wife or partner (4)
I believe the answer is:
'partner' is the definition.
(I've seen this in another clue)
'silly fellow ignoring wife' is the wordplay.
'silly fellow' becomes 'wally' (wally can mean a foolish person).
'ignoring' indicates named letters should be taken away.
'wife' becomes 'w' (abbreviation).
'wally' with 'w' taken away is 'ALLY'.
'or' is the link.
(Other definitions for ally that I've seen before include "Friend and colleague" , "A friendly and reliable country" , "Colleague, confederate" , "Supporter in a conflict" , "Collaborator, affiliate" .)