Lover boy put me in a jumper (5)
I believe the answer is:
romeo
'lover boy' is the definition.
(I've seen this before)
'me in a jumper' is the wordplay.
'in' is an insertion indicator.
'a jumper' becomes 'roo' (I've seen this before).
'me' going inside 'roo' is 'ROMEO'.
'put' is the link.
(Other definitions for romeo that I've seen before include "Lover of Juliet" , "Casanova" , "24's lover" , "Tragic Shakespeare hero" , "Lover; R (radio comms.)" .)