Beating for the endless thieving (9)
I believe the answer is:
throbbing
'beating' is the definition.
(throbbing is a kind of beating)
'the endless thieving' is the wordplay.
'endless' means to remove the last letter.
'thieving' becomes 'robbing' (robbing is a kind of thieving).
'the' with its final letter taken away is 'th'.
'th'+'robbing'='THROBBING'
'for' is the link.
(Other definitions for throbbing that I've seen before include "Pulsating" , "Beating" .)