Money study, ultimately dreary (5)
I believe the answer is:
ready
'money' is the definition.
(thesaurus)
'study ultimately dreary' is the wordplay.
'study' becomes 'read' ('read' can be a synonym of 'study').
'ultimately' suggests the final letters.
The final letter of 'dreary' is 'y'.
'read'+'y'='READY'
(Other definitions for ready that I've seen before include "In addition" , "Suitably prepared" , "Quick" , "rough companion" , "Fully prepared" .)