When to cut green targets for idiot (7)
I believe the answer is:
jackass
'for idiot' is the definition.
(I've seen this before)
'when to cut green targets' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'to cut' means one lot of letters goes inside another (some letters cut their way into a word).
'green targets' becomes 'jacks' (I can't justify this - if you can you should give a lot more credence to this answer).
'as' placed inside 'jacks' is 'JACKASS'.
Can you help me to learn more?
(Other definitions for jackass that I've seen before include "One may lark about" , "Asinine person" , "Male donkey - fool" , "Male donkey; idiot" , "See 7" .)