Heartless scoundrel regularly failing to turn up (4)
I believe the answer is:
curl
'turn up' is the definition.
'curl' can be an answer for 'turn' (thesaurus). I'm not certain of the 'up' bit.
'heartless scoundrel regularly failing' is the wordplay.
I cannot really understand how this works, but
'scoundrel' could be 'cur' (I've seen this before) and 'cur' is found in the answer.
A single letter 'l' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'to' is the link.
(Other definitions for curl that I've seen before include "Coil, ringlet" , "Coiled lock of hair" , "Force into a spiral" , "Play on ice" , "Hair piece; flick up" .)