Briefly spray a lilac (7)
I believe the answer is:
syringa
'lilac' is the definition.
(I know that lilac can be written as Syringa)
'briefly spray a' is the wordplay.
'briefly' means to remove the last letter.
'spray' becomes 'syringe' (syringing is a kind of spraying).
'syringe' with its final letter removed is 'syring'.
'syring'+'a'='SYRINGA'
(Other definitions for syringa that I've seen before include "Mock orange, lilac" , "Genus of flowering plants" , "Lilac (popularly, orange blossom)" , "Flowering shrub" , "Mock-orange plant" .)