Heard bell tolling for Ms Gwyn? (4)
I believe the answer is:
nell
'ms gwyn?' is the definition.
(Nell Gwyn, mistress of Charles II)
'heard bell tolling' is the wordplay.
'heard' shows a homophone (sound like).
'bell tolling' becomes 'knell' (the sound of a bell).
'knell' is a homophone of 'NELL'.
'for' acts as a link.
(Other definitions for nell that I've seen before include "Orphan girl" , "Dickensian heroine" , "- - Gwynne" , "-- Gwyn, 17th-century actress" , "Little --; -- Gwyn" .)