Flustered, that woman interrupts heartless song (7)
I believe the answer is:
dithery
'flustered' is the definition.
(I've seen this in another clue)
'woman interrupts heartless song' is the wordplay.
'woman' becomes 'her' (her refers to a woman).
'interrupts' indicates putting letters inside.
'heartless' means to remove the middle letters.
'song' becomes 'ditty' (ditty is a kind of song).
'ditty' with its centre removed is 'dity'.
'her' inserted within 'dity' is 'DITHERY'.
'that' is the link.
(Other definitions for dithery that I've seen before include "Unsure" , "Hesitating" , "Uncertain" , "Indecisive" , "Hesitant" .)