True love's last kiss, pretence (5)
I believe the answer is:
exact
'true' is the definition.
(thesaurus)
'love's last kiss pretence' is the wordplay.
'last' says to take the final letters.
'kiss' becomes 'x' (X can represent a kiss).
'pretence' becomes 'act'.
The final letter of 'love' is 'e'.
'e'+'x'+'act'='EXACT'
(Other definitions for exact that I've seen before include "On the nail" , "Precisely correct" , "Demand and obtain" , "accurate in all details" , "Rigorous" .)