Rubbish cut by editor — he’s beginning to be very good (3-3)
I believe the answer is:
red-hot
'be very good' is the definition.
(I've seen this before)
'rubbish cut by editor he's beginning' is the wordplay.
'rubbish' becomes 'rot' (I've seen this before).
'cut by' means one lot of letters goes inside another.
'editor' becomes 'ed'.
'beginning' says to take the initial letters.
The first letter of 'hes' is 'h'.
'ed'+'h'='edh'
'rot' going around 'edh' is 'RED-HOT'.
'to' is the link.
(Other definitions for red-hot that I've seen before include "Very recent - very sexy" , "Very exciting - glowing" , "The rod (anag.)" , "So fresh it burns - like news scoop" , "Most recent - glowing" .)