Called in a time back to categorise (7)
I believe the answer is:
arrange
'categorise' is the definition.
(thesaurus)
'called in a time back' is the wordplay.
'called' becomes 'rang' (called on the phone).
'in' means one lot of letters goes inside another.
'a time' becomes 'era' (an era is a period of time).
'back' is a reversal indicator.
'era' backwards is 'are'.
'rang' going inside 'are' is 'ARRANGE'.
'to' is the link.
(Other definitions for arrange that I've seen before include "Orchestrate - order" , "Put in order; plan" , "Put in neat order" , "Set in order" , "Sort" .)