Horse sucks energy from flower (4)
I believe the answer is:
pony
'horse' is the definition.
(pony is a kind of horse)
'sucks energy from flower' is the wordplay.
I cannot really see how this works, but
'flower' could be 'po' (Po is an example) and 'po' is found in the answer.
The remaining letters 'ny' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
(Other definitions for pony that I've seen before include "Horse (worth GBP25?)" , "Twenty-five pounds; small horse" , "staked 25" , "Sum of 25 (Informal)" , "(girl's pet, perhaps)" .)