Referring to going after old lover as 'thrilling' (8)
I believe the answer is:
exciting
'thrilling' is the definition.
(similar in meaning)
'referring to going after old lover' is the wordplay.
'referring to' becomes 'citing' ('cite' can be a synonym of 'refer to').
'going after' means one lot of letters go next to another.
'old lover' becomes 'ex' (an ex-lover).
'citing' put after 'ex' is 'EXCITING'.
'as' is the link.
(Other definitions for exciting that I've seen before include "Causing much enthusiasm" , "Stimulating, stirring" , "Arousing thrill or expectation" , "Dramatic" , "stirring things up!" .)