Sweetheart seen on pole, naked (4)
I believe the answer is:
bare
'naked' is the definition.
('bare' can be a synonym of 'naked')
'sweetheart seen on pole' is the wordplay.
'sweetheart' becomes 'e' (the heart/centre of 'sweet').
'seen on' is a charade indicator (letters next to each other).
'pole' becomes 'bar' (I've seen this before**).
'e' after 'bar' is 'BARE'.
(Other definitions for bare that I've seen before include "Unclad" , "Not covered" , "Unadorned - naked" , "Without protective covering" , "Mere" .)