Small canine (6)
(Other definitions for lapdog that I've seen before include "One readily submitting" , "devoted supporter" , "lackey" , "little pet" , "Pom, for one" .)
'small canine' is the definition.
(short for Pekingese; 'small' indicates a short form)
This is all the clue.
(Other definitions for peke that I've seen before include "In short, it's a small short-legged dog" , "Breed of dog (shortened)" , "Small dog (colloq.)" , "5 [MANS BEST FRIEND]" , "Small canine" .)