Forget holiday (5)
I believe the answer is:
leave
I believe this is a double definition.
'forget' is the first definition.
(synonyms)
'holiday' is the second definition.
(I've seen this before)
(Other definitions for leave that I've seen before include "Permission (to take holidays?)" , "Brexit's aim" , "ditch" , "Abandon" , "Quit; permission" .)