Times in the morning claiming payment back for power unit (8)
I believe the answer is:
megawatt
'for power unit' is the definition.
(megawatt is a kind of power unit)
'times in the morning claiming payment back' is the wordplay.
'times' becomes 'tt' (two abbreviations for time).
'in the morning' becomes 'am' (AM on a clock).
'claiming' indicates putting letters inside.
'payment' becomes 'wage' (wage is a kind of payment).
'back' is a reversal indicator.
'tt'+'am'='ttam'
'ttam' enclosing 'wage' is 'ttawagem'.
'ttawagem' in reverse letter order is 'MEGAWATT'.
(Other definitions for megawatt that I've seen before include "Unit of electrical power" , "measure of power" .)