Spot aim that's developed in painting technique (7)
I believe the answer is:
impasto
'painting technique' is the definition.
(I've seen this before)
'spot aim that's developed' is the wordplay.
'that's developed' is an anagram indicator.
'spot'+'aim'='spotaim'
'spotaim' is an anagram of 'IMPASTO'.
'in' is the link.
(Other definitions for impasto that I've seen before include "Thickly-applied painting technique" , "Thickly-applied paint" , "Technique of paint applied thickly" , "artistic technique" , "Slapping paint on" .)