Small label for men only (4)
I believe the answer is:
stag
'men only' is the definition.
(as in a stag do)
'small label' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'label' becomes 'tag' (synonyms).
's'+'tag'='STAG'
'for' acts as a link.
(Other definitions for stag that I've seen before include "Male beast" , "One who speculates" , "Male deer; speculator" , "in a rut, perhaps?" , "Stock market speculator" .)