Arouse trendy sweetheart (7)
I believe the answer is:
inflame
'arouse' is the definition.
(inflaming is a kind of arousing)
'trendy sweetheart' is the wordplay.
'trendy' becomes 'in' ('in' can mean fashionable).
'sweetheart' becomes 'flame' (I've seen this in another clue).
'in'+'flame'='INFLAME'
(Other definitions for inflame that I've seen before include "Bother" , "fan" , "Be provocative" , "Exacerbate" , "Incite" .)