Observed it's mottled (7)
I believe the answer is:
spotted
I believe this clue is a double definition.
'observed' is the first definition.
(I've seen this before)
'it's mottled' is the second definition.
(thesaurus)
(Other definitions for spotted that I've seen before include "- Dog; - dick" , "Caught sight of; dotty" , "Saw; mottled" , "Espied" , "Dappled - saw" .)