Tidying mop up, trim unplanned (9)
I believe the answer is:
impromptu
'unplanned' is the definition.
(I've seen this before)
'tidying mop up trim' is the wordplay.
'tidying' is an anagram indicator.
'mop'+'up'+'trim'='mopuptrim'
'mopuptrim' with letters rearranged gives 'IMPROMPTU'.
(Other definitions for impromptu that I've seen before include "On the spur of the moment" , "unrehearsed piece" , "Without much planning" , "Spontaneous" , "Unplanned; unrehearsed" .)