Caught non-drinker entering requirement (6)
I believe the answer is:
netted
'caught' is the definition.
(netting is a kind of catching)
'non-drinker entering requirement' is the wordplay.
'non drinker' becomes 'tt' (Teetotaller abbreviation).
'entering' is an insertion indicator.
'requirement' becomes 'need' ('need' can be a synonym of 'requirement').
'tt' put inside 'need' is 'NETTED'.
(Other definitions for netted that I've seen before include "As a whole" , "Caught fish, perhaps, and made clear profit" , "Gained as profit" , "Caught (like butterfly)" , "Trapped" .)