Last ones....
18d Given assistance kept going round gym (6)
I have: ?E?P?D
If the answer is HELPED, I can see that kept going might be LP (long playing but can't see where gym fits in.
17a Horse, one kept by big man (6)
I have: ?U?H?E
13a Animated feline's nibbled old garments
I have: ?O?C?A?S
If topcoats - I can understand the coats bit ie cats with the 'nibbled' o in it but what about the TOP bit?