Appropriate line in revolutionary plan (4)
I believe the answer is:
palm
'appropriate' is the definition.
(thesaurus)
'line in revolutionary plan' is the wordplay.
'line' becomes 'l'.
'in' is an insertion indicator.
'revolutionary' says the letters should be written backwards.
'plan' becomes 'map' (I've seen this before).
'map' back-to-front is 'pam'.
'l' going inside 'pam' is 'PALM'.
(Other definitions for palm that I've seen before include "Conceal magician" , "Obscure" , "Date-tree" , "Secretly snatch" , "Conceal in the hand" .)