Gent finally turned on - seeing a bit of leg (5)
I believe the answer is:
thigh
'a bit of leg' is the definition.
('thigh' is part of 'leg')
'gent finally turned on' is the wordplay.
'finally' suggests the final letters.
'turned on' becomes 'high' (both can mean excited).
The final letter of 'gent' is 't'.
't'+'high'='THIGH'
'seeing' acts as a link.
(Other definitions for thigh that I've seen before include "Part of member" , "top of pin" , "Upper part of the leg" , "Femoral leg part" , "Upper joint of the leg" .)