Inspired by Red Sea - Queen's getting rest (9)
I believe the answer is:
remainder
'rest' is the definition.
(I know that rest can be written as remainder)
'inspired by red sea queen's' is the wordplay.
'inspired by' is an insertion indicator (some letters breathed in or 'inspired' by others).
'sea' becomes 'main' (synonyms).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'red' enclosing 'main' is 'remaind'.
'remaind'+'er'='REMAINDER'
'getting' acts as a link.
(Other definitions for remainder that I've seen before include "Surplus" , "deposit" , "Rest - sell off (books) cheap" , "part that is still to come" , "Left-over" .)