Expert paid arsonist from time to time (6)
I believe the answer is:
adroit
'expert' is the definition.
(thesaurus)
'paid arsonist from time to time' is the wordplay.
'from time to time' indicates alternate letters (letters removed on a regular basis).
'paid'+'arsonist'='paidarsonist'
The alternate letters of 'paidarsonist' are 'ADROIT'.
(Other definitions for adroit that I've seen before include "Skilful or ingenious" , "Quick and clever in action or thought" , "Skilled" , "Skilful, expert" , "Quick-witted" .)