Pose kept up by horse flogger (9)
I believe the answer is:
chastiser
'flogger' is the definition.
(someone who chastises or flogs someone)
'pose kept up by horse' is the wordplay.
I cannot really see how this works, but
'up' could be 'is' (I've seen this in other clues) and 'is' is located in the answer.
'horse' could be 'h' (abbreviation as in horse power) and 'h' is located in the answer.
The remaining letters 'caster' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for chastiser that I've seen before include "smacker" , "One strapping" , "One who severely reprimands" .)