Romeo needs help in attack (4)
I believe the answer is:
raid
'attack' is the definition.
(raid is a kind of attack)
'romeo needs help' is the wordplay.
'romeo' becomes 'R' (phonetic alphabet: alpha, bravo, charlie etc.).
'needs' is a charade indicator (letters next to each other).
'help' becomes 'aid' (synonyms).
'r'+'aid'='RAID'
'in' is the link.
(Other definitions for raid that I've seen before include "Search by police without warning" , "Invasion" , "Foray, sudden attack" , "Assault, attack" , "Go on the attack" .)