Difficult friend had food somewhere in his mouth (4,6)

'somewhere in his mouth' is the definition.
The definition and answer can be both body parts as well as being singular nouns.
Maybe you can see a link between them that I don't see?

'difficult friend had food' is the wordplay.
'difficult' becomes 'hard' (associated in meaning).
'friend' becomes 'pal' (pal can mean a friend).
'had food' becomes 'ate' (to eat is to have some food).
'hard'+'pal'+'ate'='HARD PALATE'

Can you help me to learn more?