Be servile (6)
I believe the answer is:
kowtow
'be servile' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for kowtow that I've seen before include "Chinese submissive gesture" , "Lick someone's boots" , "Toady" , "Grovel in old Peking" , "Gesture of submission" .)