Fuel pumps filling dropped air intakes (5)
I believe the answer is:
gasps
'dropped air intakes' is the definition.
The definition and answer can be both acts as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'fuel pumps filling' is the wordplay.
'fuel' becomes 'gas' (gas is a kind of fuel).
'pumps filling' becomes 'ps' (I am not sure about this - if you are sure you should believe this answer much more).
'gas'+'ps'='GASPS'
Can you help me to learn more?
(Other definitions for gasps that I've seen before include "Draws breath sharply" , "'Pants, puffs (5)'" .)