Small bottle left by a whip (7)
I believe the answer is:
scourge
'whip' is the definition.
(I know that scourge is a type of whip)
'small bottle left by a' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'bottle' becomes 'courage' (I've seen this before).
'left by' indicates named letters should be taken away (word is left or abandoned by specified letters ).
'courage' with 'a' taken away is 'courge'.
's'+'courge'='SCOURGE'
(Other definitions for scourge that I've seen before include "torment" , "Source of great trouble" , "Plague; whip" , "cat" , "One causing great suffering; whip" .)