Dog leaps in explosively (7)
I believe the answer is:
spaniel
'dog' is the definition.
(spaniel is a kind of dog)
'leaps in explosively' is the wordplay.
'explosively' is an anagram indicator.
'leaps'+'in'='leapsin'
'leapsin' anagrammed gives 'SPANIEL'.
(Other definitions for spaniel that I've seen before include "Breed of dog" , "Alpines (anag)" , "See 13" , "Dog found among the alpines" , "Springer- - -" .)