Take on a high-sounding army corps (4)
I believe the answer is:
hire
'take on' is the definition.
(thesaurus)
'a high-sounding army corps' is the wordplay.
'sounding' indicates a 'sounds like' (homophone) clue.
'army corps' becomes 're' (I've seen this in other clues).
'high' sounds like 'hi'.
'hi'+'re'='HIRE'
(Other definitions for hire that I've seen before include "Pay for temporary use" , "Pay to use something" , "Employ (for wages)" , "Charter, employ" , "Rent, employ" .)