Dog jumps about, entertaining half of nick (7)
I believe the answer is:
spaniel
'dog' is the definition.
(spaniel is a kind of dog)
'jumps about entertaining half of nick' is the wordplay.
'jumps' becomes 'leaps' (leap is a kind of jump**).
'about' is a reversal indicator.
'entertaining' is an insertion indicator.
'half of' means to take half the letters.
'leaps' written backwards gives 'spael'.
'nick' halved is 'ni'.
'spael' placed around 'ni' is 'SPANIEL'.
(Other definitions for spaniel that I've seen before include "Dog - leaps in (anag)" , "Alpines (anag)" , "Droopy-eared dog" , "[HOUND]" , "Breed of dog" .)