Sleuth left very little to get his teeth into (6)
I believe the answer is:
morsel
'very little to get his teeth into' is the definition.
(a morsel is a small amount of food)
'sleuth left' is the wordplay.
'sleuth' becomes 'Morse' (fictional detective Inspector Morse).
'left' becomes 'l' (common abbreviation).
'morse'+'l'='MORSEL'
(Other definitions for morsel that I've seen before include "a little food" , "Titbit" , "Crumb" , "Tiny piece" , "Small amount of food, a bite" .)