Fool taking a step back (3)
I believe the answer is:
sap
'fool' is the definition.
(synonyms)
'a step back' is the wordplay.
'a step' becomes 'pas' (I've seen this in another clue).
'back' is a reversal indicator.
'pas' backwards is 'SAP'.
'taking' acts as a link.
(Other definitions for sap that I've seen before include "Undermine; fool" , "trench used in siege" , "Insidiously undermine" , "Moisture in wood of a tree" , "Plant liquid or general vitality" .)