Conclude with passion, suggesting a truce (9)
I believe the answer is:
ceasefire
'a truce' is the definition.
(I've seen this before)
'conclude with passion' is the wordplay.
'conclude' becomes 'cease' (I've seen this in another clue).
'with' says to put letters next to each other.
'passion' becomes 'fire' (fire is a kind of passion).
'cease'+'fire'='CEASEFIRE'
'suggesting' acts as a link.
(Other definitions for ceasefire that I've seen before include "Break in fighting" , "Truce" .)