Son cheer for only fish? (4)
I believe the answer is:
sole
'only fish?' is the definition.
(I've seen this in another clue)
'son cheer' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'cheer' becomes 'ole' (I have seen 'Spanish cheer ' mean 'ole' so perhaps 'cheer' could also mean 'ole').
's'+'ole'='SOLE'
'for' is the link.
(Other definitions for sole that I've seen before include "Just one - fish" , "Exclusive class of fish" , "piece of leather" , "Dover - -" , "Shoe part -- lone" .)