Sagging (6)
I believe the answer is:
droopy
'sagging' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for droopy that I've seen before include "Hanging limply - animated dog created by Tex Avery" , "Tending to 27 [SAG]" , "Lacking strength" , "Cartoon poodle" , "Cartoon dog - sagging" .)