Nerd with gin collapsed and smiled (7)
I believe the answer is:
grinned
'smiled' is the definition.
(grinning is a kind of smiling)
'nerd with gin collapsed' is the wordplay.
'with' is a charade indicator (letters next to each other).
'collapsed' indicates an anagram.
'nerd' after 'gin' is 'ginnerd'.
'ginnerd' anagrammed gives 'GRINNED'.
'and' is the link.
(Other definitions for grinned that I've seen before include "was amused" , "Smiled broadly" .)