Trimmed, pale olive-coloured sacs (7)
I believe the answer is:
alveoli
'sacs' is the definition.
The definition and answer can be both body parts as well as being plural nouns.
Maybe you can see a link between them that I can't see?
'trimmed pale olive-coloured' is the wordplay.
'trimmed' says to take the centre (the external letters are trimmed from the word).
'coloured' indicates anagramming the letters.
The centre of 'pale' is 'al'.
'olive' with letters rearranged gives 'veoli'.
'al'+'veoli'='ALVEOLI'
Can you help me to learn more?
(Other definitions for alveoli that I've seen before include "Bit of lung" , "Parts of lungs" , "Sockets for tooth roots" , "providing lung processes" .)