Take a look back, as retainers do (4)
I believe the answer is:
keep
'take' is the definition.
(I know that take is a more specific form of the action enter)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for keep that I've seen before include "Observe - reserve - preserve" , "honour" , "Remain" , "Conserve" , "Retain; stronghold" .)