Moved quickly into outfit valuing intelligence – they are full of brains (6)

'full of brains' is the definition.
The answer and definition can be both body parts as well as being plural nouns.
Perhaps you can see an association between them that I don't see?

'moved quickly into outfit valuing intelligence they' is the wordplay.
I cannot really understand how this works, but
'moved' could be 'ran' ('run' can be a synonym of 'move') and 'ran' is found within the answer.
'intelligence' could be 'cia' (Central Intelligence Agency) and 'cia' is located in the remaining letters.
No letters remain.
This explanation may well be incorrect...

'are' acts as a link.

Can you help me to learn more?