Avoids, when skirting the green (6)
I believe the answer is:
averts
'avoids' is the definition.
(I know this)
'when skirting the green' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'skirting' means one lot of letters goes inside another.
'the green' becomes 'vert' (heraldic term for green).
'as' placed around 'vert' is 'AVERTS'.
(Other definitions for averts that I've seen before include "Wards off" , "Deflects, heads off" , "Turns aside" , "Heads off, prevents from happening" , "Of eyes or gaze, turns away" .)