Allen at the start breaks cue and rest (9)
I believe the answer is:
remainder
'rest' is the definition.
(synonyms)
'allen at the start breaks cue' is the wordplay.
I cannot quite understand how this works, but
'at' could be 'in' and 'in' is located in the answer.
This explanation may well be incorrect...
'and' acts as a link.
Can you help me to learn more?
(Other definitions for remainder that I've seen before include "Rest - sell off (books) cheap" , "book going cheap" , "Left-over" , "Unsold book; rest" , "butt" .)