Opportunity provides one (4)
I believe the answer is:
unit
'one' is the definition.
('unit' can be a synonym of 'one')
'opportunity provides' is the wordplay.
'provides' says the answer is hidden in the clue.
'UNIT' is hidden within 'opportunity'.
(Other definitions for unit that I've seen before include "Single item, maybe part of a set" , "Item combining separate parts" , "Subdivision of a military group" , "Military team" , "Body of soldiers" .)