I would set about getting hold of fashionable garment (5)
I believe the answer is:
dhoti
'garment' is the definition.
(dhoti is a kind of garment)
'i would set about getting hold of fashionable' is the wordplay.
'i would' becomes 'I'd'.
'set about' says the letters should be written backwards.
'getting hold of' indicates putting letters inside.
'fashionable' becomes 'hot' (I've seen this in another clue).
'id' reversed gives 'di'.
'di' placed around 'hot' is 'DHOTI'.
(Other definitions for dhoti that I've seen before include "garment in India" , "article of clothing" , "Hindu loincloth" , "Skimpy item of clothing" , "Lean over; end of loaf" .)