Dandy joins apple hunt (7)
I believe the answer is:
coxcomb
'dandy' is the definition.
(both can mean a vain man)
'joins apple hunt' is the wordplay.
'joins' says to put letters next to each other.
'apple' becomes 'cox' (type of apple).
'hunt' becomes 'comb' (both can mean to search for something).
'cox' put next to 'comb' is 'COXCOMB'.
(Other definitions for coxcomb that I've seen before include "Conceited dandy" , "Fleshy red crest on a cock's head" , "rather vain fellow" , "Fool" , "Red crest on the head of the domestic fowl" .)