As in general revolving frame (5)
I believe the answer is:
'frame' is the definition.
(I've seen this before)
'as in general revolving' is the wordplay.
'in' is an insertion indicator.
'general' becomes 'lee' (Robert E. Lee - US revolutionary commander).
'revolving' says the letters should be written backwards.
'lee' in reverse letter order is 'eel'.
'as' going into 'eel' is 'EASEL'.
(Other definitions for easel that I've seen before include "Artist's equipment" , "dead-headed plant" , "Blackboard supporter" , "art supporter" , "Support for 12's [ARTIST]" .)