Independent setter interrupted by a good idea (5)
I believe the answer is:
image
'idea' is the definition.
(I've seen this in another clue)
'independent setter interrupted by a good' is the wordplay.
'independent' becomes 'i'.
'setter' becomes 'me' (the setter of the clue).
'interrupted by' means one lot of letters goes inside another.
'good' becomes 'g' (abbreviation).
'a'+'g'='ag'
'me' placed around 'ag' is 'mage'.
'i'+'mage'='IMAGE'
(Other definitions for image that I've seen before include "personality" , "Reflection" , "Likeness; statue" , "Vision" , "Representation, picture" .)