Make tracks opening for Hothouse Flower briefly on first night (6)
I believe the answer is:
hasten
'make tracks' is the definition.
(I've seen this in another clue)
'opening for hothouse flower briefly on first night' is the wordplay.
'opening for' says to take the initial letters.
'flower' becomes 'aster ' (type of flower).
'briefly' means to remove the last letter.
'on' is a charade indicator (letters next to each other).
'first night' becomes 'n' (1st letter of 'night').
The initial letter of 'hothouse' is 'h'.
'aster' with its final letter taken off is 'aste'.
'h'+'aste'+'n'='HASTEN'
(Other definitions for hasten that I've seen before include "race? - with 26a" , "Travel with expedition" , "dash" , "Act or move fast" , "Rush" .)