Resilient young male worker inspiring union leader (7)
I believe the answer is:
buoyant
'resilient' is the definition.
('buoyant' can be a synonym of 'resilient')
'young male worker inspiring union leader' is the wordplay.
'young male' becomes 'boy' (I've seen this before).
'worker' becomes 'ant' (worker is a type of ant).
'inspiring' is an insertion indicator.
'leader' suggests taking the first letters.
The initial letter of 'union' is 'u'.
'boy'+'ant'='boyant'
'boyant' placed around 'u' is 'BUOYANT'.
(Other definitions for buoyant that I've seen before include "Floatable" , "Bouncy" , "Lively nineteen twenties dance" , "refusing to go to bed?" , "In good spirits" .)