Look for overthrown strongholds yielding power (4)
I believe the answer is:
seek
'look for' is the definition.
('seek' can be a synonym of 'look for')
'overthrown strongholds yielding power' is the wordplay.
'overthrown' is a reversal indicator.
'strongholds' becomes 'keeps' (keep is a kind of stronghold).
'yielding' suggests deleting specific letters.
'power' becomes 'p'.
'keeps' with 'p' removed is 'kees'.
'kees' in reverse letter order is 'SEEK'.
(Other definitions for seek that I've seen before include "Try to find" , "Try to locate or reach" , "Ask for (permission)" , "Hunt, look for" , "Attempt - search" .)