Secretary, say, returning call (4)
I believe the answer is:
page
'call' is the definition.
(thesaurus)
'secretary say returning' is the wordplay.
'secretary' becomes 'pa' (I've seen this in other clues).
'say' becomes 'eg'.
'returning' shows that the letters should be reversed in order.
'eg' back-to-front is 'ge'.
'pa'+'ge'='PAGE'
(Other definitions for page that I've seen before include "Youth acting as a knight's attendant" , "Leaf - boy attendant" , "Summon" , "one seeking knighthood" , "Piece of paper for a young attendant" .)