Be prepared to surround (5)
I believe the answer is:
beset
'to surround' is the definition.
(I've seen this in another clue)
'be prepared' is the wordplay.
'prepared' becomes 'set' (set up or ready).
'be'+'set'='BESET'
(Other definitions for beset that I've seen before include "Press" , "Plagued" , "Surround (with problems)" , "Beleaguer" , "Hemmed in, afflicted with" .)