The right help in a surprise attack (4)
I believe the answer is:
raid
'a surprise attack' is the definition.
(I've seen this before)
'the right help' is the wordplay.
'the right' becomes 'r' (common abbreviation).
'help' becomes 'aid' (synonyms).
'r'+'aid'='RAID'
'in' acts as a link.
(Other definitions for raid that I've seen before include "bust" , "Stock Exchange activity" , "Foray, sudden attack" , "A sudden military attack and withdrawal" , "Rifle" .)