Is suspicious when department head is seen meeting charitable institutions (9)

'charitable institutions' is the definition.
Although both the answer and definition are plural nouns, I don't understand how they can define each other.

'is suspicious when department head is seen' is the wordplay.
I cannot really understand how this works, but
'is' is present in the answer.
'department' could be 'd' (abbreviation eg in MOD Ministry of Defence) and 'd' is present in the answer.
The remaining letters 'trusts' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

'meeting' acts as a link.

Can you help me to learn more?