Privileged when 50 per cent feasible (8)
I believe the answer is:
enviable
'privileged' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I can't see?
'when 50 per cent feasible' is the wordplay.
'when' becomes 'e' (I've seen this in other clues).
'50 per cent' becomes 'n' (I can't explain this - if you can you should believe this answer much more).
'feasible' becomes 'viable' (synonyms).
'e'+'n'+'viable'='ENVIABLE'
Can you help me to learn more?
(Other definitions for enviable that I've seen before include "Desirable enough to make one green-eyed" , "sought-after" , "Much to be desired" , "Causing a desire to have what another has" , "Likely to cause jealousy" .)