Rascal finishing in store (9)
I believe the answer is:
impending
'in store' is the definition.
(thesaurus)
'rascal finishing' is the wordplay.
'rascal' becomes 'imp' ('imp' can be a synonym of 'rascal').
'finishing' becomes 'ending' ('end' can be a synonym of 'finish').
'imp'+'ending'='IMPENDING'
(Other definitions for impending that I've seen before include "Looming" , "coming?" , "About to happen" , "Threatening" .)