Foppish fellow also losing head (5)
I believe the answer is:
swell
'foppish fellow' is the definition.
(swell can mean a fashionable person)
'also losing head' is the wordplay.
'also' becomes 'as well' (synonyms).
'losing head' means to remove the first letter.
'aswell' with its initial letter taken away is 'SWELL'.
(Other definitions for swell that I've seen before include "Informally good, grow larger" , "Balloon - movement of the sea's surface" , "Bulge; a toff" , "wonderful" , "Gentle sea movement" .)