Concentrate on heart of best sort of scene (7)
I believe the answer is:
essence
'concentrate' is the definition.
(I've seen this before)
'heart of best sort of scene' is the wordplay.
'heart of' indicates the central letters.
'sort of' indicates an anagram.
The central letters of 'best' are 'es'.
'scene' with letters rearranged gives 'sence'.
'es'+'sence'='ESSENCE'
'on' is the link.
(Other definitions for essence that I've seen before include "one of 21 [HEARTS]" , "Fundamental nature or quality" , "Basic quality" , "Perfume or concentrate" , "Plant extract flavouring" .)