Rapidly recruiting US taxmen for high-level domain? (8)
I believe the answer is:
airspace
'taxmen for high-level domain?' is the definition.
I can't tell whether this defines the answer.
'rapidly recruiting us' is the wordplay.
'rapidly' becomes 'apace' (synonyms).
'recruiting' indicates putting letters inside (inserted letters are recruited into the word).
'us' becomes 'irs' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'apace' placed around 'irs' is 'AIRSPACE'.
Can you help me to learn more?
(Other definitions for airspace that I've seen before include "What pilot goes through" , "Atmosphere over (area of) earth" , "Here planes fly" .)