Former deputy making rigorous demands (8)
I believe the answer is:
exacting
'making rigorous demands' is the definition.
(I've seen this before)
'former deputy' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'deputy' becomes 'acting' (I've seen this in other clues).
'ex'+'acting'='EXACTING'
(Other definitions for exacting that I've seen before include "Insisting upon" , "Making great demands, requiring real effort" , "Stringent" , "Arduous and demanding" , "Making rigorous demands" .)