Supporter, strangely heartened, dropping an E (8)
I believe the answer is:
adherent
'supporter' is the definition.
(I've seen this before)
'strangely heartened dropping an e' is the wordplay.
'strangely' indicates anagramming the letters.
'dropping' suggests deleting specific letters.
'heartened' with 'e' removed is 'hartened'.
'hartened' with letters rearranged gives 'ADHERENT'.
(Other definitions for adherent that I've seen before include "sticker" , "Person supporting" , "Supporter, fan" , "Loyal follower, one who sticks" , "Follower, partisan" .)