Socially inept fellow participating in dinner-dance (4)
I believe the answer is:
nerd
'socially inept fellow' is the definition.
'participating in dinner-dance' is the wordplay.
'participating in' says the answer is hidden in the clue.
'NERD' is hidden in the letters of 'dinner dance'.
(Other definitions for nerd that I've seen before include "Student who is ridiculed for studying excessively" , "Sort of chap" , "Socially inept but knowledgeable person" , "Studious bore" , "Intelligent but single-minded expert" .)