Condescend to remove an old feature of organ (4)
I believe the answer is:
stop
'feature of organ' is the definition.
(a musical organ contains stops)
'condescend to remove an old' is the wordplay.
'condescend' becomes 'stoop' (I've seen this before).
'to remove' is a deletion indicator.
'an old' becomes 'o' (common abbreviation eg in OE for Old English).
'stoop' with 'o' removed is 'STOP'.
(Other definitions for stop that I've seen before include "Block; end; group of organ pipes" , "Blockage" , "colon, say" , "Refrain from" , "period in US" .)