Singular label for men only (4)
I believe the answer is:
stag
'men only' is the definition.
(I've seen this before)
'singular label' is the wordplay.
'singular' becomes 's' (abbreviation sometimes used in dictionaries).
'label' becomes 'tag' ('tag' can be a synonym of 'label'**).
's'+'tag'='STAG'
'for' acts as a link.
(Other definitions for stag that I've seen before include "Male at party?" , "in a rut, perhaps?" , "Antlered beast" , "speculator wanting quick profit" , "Men-only" .)