Suffering over love is welcome (5)
I believe the answer is:
hello
'is welcome' is the definition.
(both are greetings)
'suffering over love' is the wordplay.
'suffering' becomes 'hell' (hell can mean a terrible ordeal).
'over' says to put letters next to each other.
'love' becomes 'o' (love means zero in tennis).
'hell'+'o'='HELLO'
(Other definitions for hello that I've seen before include "Conversation starter" , "Look at that" , "Expression of greeting" , "Welcome" , "opener?" .)