Runs to help in attack (4)
I believe the answer is:
raid
'attack' is the definition.
(raid is a kind of attack)
'runs to help' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'to help' becomes 'aid' ('aid' can be a synonym of 'help').
'r'+'aid'='RAID'
'in' acts as a link.
(Other definitions for raid that I've seen before include "A sudden military attack and withdrawal" , "Stock Exchange activity" , "Invade" , "military operation" , "Maraud" .)