Dry? Knock back spirits, raised before going out (7)
I believe the answer is:
parched
'dry?' is the definition.
(thesaurus)
'knock back spirits raised before going out' is the wordplay.
'knock' becomes 'rap' ('rap' can be a synonym of 'knock'**).
'back' says the letters should be written in reverse.
'spirits raised' becomes 'cheered'.
'before' becomes 'ere' (usually literary).
'going out' indicates named letters should be taken away.
'rap' written backwards gives 'par'.
'cheered' with 'ere' removed is 'ched'.
'par'+'ched'='PARCHED'
(Other definitions for parched that I've seen before include "Made dry and thirsty" , "Extremely dry" , "Deprived of water" , "Dried out by heat" .)