Queen in Australia rising for nothing (4)
I believe the answer is:
zero
'nothing' is the definition.
(I know that nothing can be written as zero)
'queen in australia rising' is the wordplay.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'in' indicates putting letters inside.
'australia' becomes 'oz' (informal name for Australia).
'rising' says the letters should be written backwards (going up in a down clue).
'oz' written backwards gives 'zo'.
'er' put inside 'zo' is 'ZERO'.
'for' acts as a link.
(Other definitions for zero that I've seen before include "Japanese fighter" , "Loser" , "Nought, the figure 0" , "Uncompromising application of the law against antisocial behaviour" , "Nothing - Japanese aircraft" .)