Cross the new rate out - it's more to pay! (5)
I believe the answer is:
extra
'more to pay' is the definition.
I can't judge whether this defines the answer.
'cross the new rate out' is the wordplay.
'cross' becomes 'x' (an X is a cross).
'the new' indicates an anagram.
'out' is an insertion indicator.
'rate' with letters rearranged gives 'etra'.
'x' going within 'etra' is 'EXTRA'.
'it's' acts as a link.
Can you help me to learn more?
(Other definitions for extra that I've seen before include "Score not made by 34 [CRICKETER]" , "walk-on part" , "more than usually" , "23 player?" , "Bonus; supplement" .)