Anorak held by dinner date (4)
I believe the answer is:
nerd
'anorak' is the definition.
(I've seen this before)
'held by dinner date' is the wordplay.
'held by' indicates the answer is hidden within the clue.
'NERD' is hidden within 'dinner date'.
(Other definitions for nerd that I've seen before include "Flag on poles; wide (headline)" , "Someone boring (about computers?)" , "Sort of chap" , "one that's overly cerebral" , "Student who is ridiculed for studying excessively" .)