"___ Now or Never" (3)
(Other definitions for its that I've seen before include "Belonging to something nonhuman" , "The thing's" , "Belonging to a particular thing" , "Another form of 'tis" , "Neuter possessive pronoun" .)
'now or never' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for adverb that I've seen before include "twelve for example" , "Verb modifier" , "-ly word" , "Verb qualifier" , "fast, maybe?" .)