Poor cadet welcoming unlimited offer is not genuine (8)
I believe the answer is:
affected
'not genuine' is the definition.
'poor cadet welcoming unlimited offer' is the wordplay.
'poor' indicates an anagram.
'welcoming' indicates putting letters inside (in sense of 'inviting in').
'unlimited' indicates the central letters (discard the edges or 'limits' of the word).
The middle of 'offer' is 'ffe'.
'cadet' is an anagram of 'acted'.
'acted' enclosing 'ffe' is 'AFFECTED'.
'is' acts as a link.
(Other definitions for affected that I've seen before include "Given to posing, artificial in manner" , "mincing?" , "Made a difference to" , "Artificial of manner, pretentious" , "Pretentious, designed to impress" .)