Saw a little marmot today (5)
I believe the answer is:
motto
'saw' is the definition.
(thesaurus)
'a little marmot today' is the wordplay.
'a little' indicates a hidden word.
'MOTTO' can be found hidden inside 'marmot today'.
(Other definitions for motto that I've seen before include "Saw" , "Maxim; slogan" , "statement of belief" , "Message in cracker" , "Favourite saying of a group" .)