Horse backed in some difficulty - no pressure (4)
I believe the answer is:
pony
'horse' is the definition.
(pony is a kind of horse)
'backed in some difficulty no pressure' is the wordplay.
'backed' shows that the letters should be reversed in order.
'in' says the answer is hidden in the clue.
'ynop' is hidden in the letters of 'some difficulty no pressure'.
'ynop' backwards is 'PONY'.
(Other definitions for pony that I've seen before include "(girl's pet, perhaps)" , "staked 25" , "Sum of 25 (Informal)" , "Small horse - GBP25" , "Animal; PS25" .)