'Small' Conservative old females mock (5)
I believe the answer is:
scoff
'mock' is the definition.
(scoff can mean to mock or tease)
'small conservative old females' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'conservative' becomes 'C' (UK political abbreviation).
'old' becomes 'o' (abbreviation).
'females' becomes 'ff' (an abbreviation for female written twice).
's'+'c'+'o'+'ff'='SCOFF'
(Other definitions for scoff that I've seen before include "turtle soup for example?" , "Jeer; eat greedily" , "Mock" , "Ridicule - guzzle" , "food on offer" .)