Manage plentiful supply in vale? (8)
I believe the answer is:
farewell
'vale?' is the definition.
('vale' means farewell in Latin)
'manage plentiful supply' is the wordplay.
'manage' becomes 'fare' (how you fare is how you manage with something).
'plentiful supply' becomes 'well' (I've seen this before).
'fare'+'well'='FAREWELL'
'in' acts as a link.
(Other definitions for farewell that I've seen before include "Archaic goodbye or leave-taking" , "Wish on leave-taking" , "Say goodbye" , "It may be said when 15" , "symphony" .)