Mystical symbol seen in peeled dried plums (4)
I believe the answer is:
rune
'mystical symbol' is the definition.
(I've seen this in another clue)
'peeled dried plums' is the wordplay.
'peeled' indicates the central letters (outer letters are peeled off).
'dried plums' becomes 'prunes' (I've seen this in another clue).
The centre of 'prunes' is 'RUNE'.
'seen in' is the link.
(Other definitions for rune that I've seen before include "Old alphabet letter" , "Ancient character" , "Ancient symbol" , "Mystical symbol" , "Early symbol used in carvings" .)