Farm animals slowly escape — hard to stop that (5)
I believe the answer is:
sheep
'farm animals slowly escape hard to stop that' is the definition.
'sheep' can be an answer for 'farm animals' (I've seen this before). I'm not certain of the remainder of the definition.
'hard to stop that' is the wordplay.
'hard' becomes 'h'.
'to stop' indicates putting letters inside.
'that' becomes 'seep' (I can't justify this - if you can you should believe this answer much more).
'h' put within 'seep' is 'SHEEP'.
Can you help me to learn more?
(Other definitions for sheep that I've seen before include "Ovine animals" , "Source of wool" , "Source of lamb" , "One lacking initiative (but better than a goat?)" , "Ruminant animal" .)