Mail perhaps from Romeo in love affair (6)
I believe the answer is:
armour
'mail perhaps' is the definition.
(mail is a kind of armour)
'romeo in love affair' is the wordplay.
'romeo' becomes 'R' (phonetic alphabet: alpha, bravo, charlie etc.).
'in' is an insertion indicator.
'love affair' becomes 'amour' (I've seen this before).
'r' put within 'amour' is 'ARMOUR'.
'from' is the link.
(Other definitions for armour that I've seen before include "Metal or chainmail suit" , "Protective body-plating" , "Suit of mail" , "Old warrior's suit" , "Body plate" .)