Corrupt mates in power (5)
I believe the answer is:
steam
'power' is the definition.
(I've seen this before)
'corrupt mates' is the wordplay.
'corrupt' is an anagram indicator.
'mates' with letters rearranged gives 'STEAM'.
'in' is the link.
(Other definitions for steam that I've seen before include "Watery vapour" , "12 dn water vapour" , "enthusiasm" , "Gas from boiliing water" , "Travel in liner" .)