Sweep a little to hide marks (5)
I believe the answer is:
ambit
'sweep' is the definition.
(thesaurus)
'a little to hide marks' is the wordplay.
'a little' becomes 'abit' (synonyms).
'to hide' indicates putting letters inside.
'marks' becomes 'M' (former German currency).
'abit' enclosing 'm' is 'AMBIT'.
(Other definitions for ambit that I've seen before include "Scope or confines" , "Scope, extent, or bounds of something" , "round" , "Limits" , "Scope or circuit" .)