Get to be moralistic when out of power (5)
I believe the answer is:
reach
'get' is the definition.
(reaching is a kind of getting)
'to be moralistic when out of power' is the wordplay.
'to be moralistic' becomes 'preach'.
'when out of' indicates named letters should be taken away.
'power' becomes 'p'.
'preach' with 'p' removed is 'REACH'.
(Other definitions for reach that I've seen before include "Open stretch of water" , "Put out the hand for a part of the river" , "Succeed in getting to" , "Arrive at the destination" , "Hit" .)