Supply air like a freebooter (8)
I believe the answer is:
aspirate
'supply air' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'like a freebooter' is the wordplay.
'like' becomes 'as'.
'a freebooter' becomes 'pirate' (pirate is a kind of freebooter).
'as'+'pirate'='ASPIRATE'
Can you help me to learn more?
(Other definitions for aspirate that I've seen before include "Breathe in; sound of h" , "First appearance of Hook" , "Hook, initially" , "Stop" , "Breathed consonant" .)