To bring back the cat is a matter of luck! (4-2)
I believe the answer is:
toss-up
'matter of luck' is the definition.
'toss-up' can be an answer for 'luck' (toss-up is a kind of luck). I am not sure about the 'matter of' bit.
'to bring back the cat' is the wordplay.
'bring back' is a reversal indicator.
'the cat' becomes 'puss' (puss is a kind of cat).
'puss' backwards is 'ssup'.
'to'+'ssup'='TOSS-UP'
'is a' acts as a link.
Can you help me to learn more?
(Other definitions for toss-up that I've seen before include "Use of a coin to choose" , "Flip of a coin" , "Fifty-fifty chance" , "It helps you pick" .)