Am I about to start on clean sort of power? (6)
I believe the answer is:
atomic
'sort of power?' is the definition.
(as in atomic power)
'am i about to start on clean' is the wordplay.
'about' is an insertion indicator.
'start on' suggests taking the first letters (I've seen 'starts on' mean this).
The first letter of 'clean' is 'c'.
'am'+'i'='ami'
'ami' placed around 'to' is 'atomi'.
'atomi'+'c'='ATOMIC'
(Other definitions for atomic that I've seen before include "Basically simple" , "Relating to basic particles" , "Energy released in nuclear fission or fusion" , "Type of energy" , "Using nuclear energy" .)