Return fan's VAT (3)
I believe the answer is:
tun
'vat' is the definition.
(I've seen this in another clue)
'return fan's' is the wordplay.
'return' says the letters should be written in reverse.
'fan' becomes 'nut' (both can mean an enthusiast).
'nut' backwards is 'TUN'.
(Other definitions for tun that I've seen before include "Container of beer" , "One can hold wine" , "Barrel holding many gallons" , "'Large cask, for beer perhaps (3)'" , "beer barrel" .)