Surround, encircle (4)
I believe the answer is:
gird
I believe this clue is a double definition.
'surround' is the first definition.
(girding is a kind of surrounding)
'encircle' is the second definition.
(synonyms)
(Other definitions for gird that I've seen before include "ring" , "Encircle - fasten with belt" , "Put a belt on" , "Surround" , "Steel" .)