Note this little lot! (5)
I believe the answer is:
minim
'note' is the definition.
(musical note)
'this little lot' is the wordplay.
'this little' becomes 'mini'.
'lot' becomes 'm'.
'mini'+'m'='MINIM'
(Other definitions for minim that I've seen before include "Quarter of a breve" , "It's a downward stroke" , "Double crotchet" , "Half-note" , "Note of two crotchets" .)