Portrait's head isn't the Queen, according to artist (7)
I believe the answer is:
painter
'artist' is the definition.
(painter is a kind of artist)
'portrait's head isn't the queen' is the wordplay.
'head' suggests taking the first letters.
'isn't' becomes 'aint' (non-standard version of 'isn't').
'the queen' becomes 'ER' (Elizabeth Regina).
The first letter of 'portraits' is 'p'.
'p'+'aint'+'er'='PAINTER'
'according to' is the link.
(Other definitions for painter that I've seen before include "Matisse, maybe" , "One of two Johns" , "Line attached to the bow of a boat when tying up" , "that may tie up a cat, perhaps?" , "Artist - rope for boat" .)