Heads for Marks and Spencer newer fancy clothing department (8)
I believe the answer is:
menswear
'clothing department' is the definition.
(type of clothing)
'heads for marks and spencer newer fancy' is the wordplay.
'heads for' indicates taking the first letters.
'fancy' is an anagram indicator.
The first letters of 'marks and spencer' is 'mas'.
'mas'+'newer'='masnewer'
'masnewer' with letters rearranged gives 'MENSWEAR'.
(Other definitions for menswear that I've seen before include "For example, ties" , "clobber" , "Ties, say" , "it covers their bodies" , "Y-fronts, among other things" .)