Affair gives rise to trouble with one lad (7)
I believe the answer is:
liaison
'affair' is the definition.
('liaison' can be a synonym of 'affair')
'rise to trouble with one lad' is the wordplay.
'rise' is a reversal indicator.
'to trouble' becomes 'ail' ('ail' can be a synonym of 'trouble').
'with' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'lad' becomes 'son'.
'ail' backwards is 'lia'.
'lia'+'i'+'son'='LIAISON'
'gives' is the link.
(Other definitions for liaison that I've seen before include "Communication between groups or units" , "Illicit romance" , "A contact or affair" , "Intermediary" , "Contact between groups" .)