In garden tree is burning (6)
I believe the answer is:
ardent
'burning' is the definition.
(both can mean passionate)
'in garden tree is' is the wordplay.
'in' says the answer is hidden in the clue.
'ARDENT' is hidden within 'garden tree is'.
(Other definitions for ardent that I've seen before include "Passionate and glowing" , "Burning, passionate" , "'Fervent, impassioned (6)'" , "Ranted badly and became earnest in love" , "Passionate, fervent" .)