About to harden, removing uniform (2,2)
I believe the answer is:
in re
'about' is the definition.
(thesaurus)
'harden removing uniform' is the wordplay.
'harden' becomes 'inure' ('inure' can be a synonym of 'harden').
'removing' indicates named letters should be taken away.
'uniform' becomes 'u' (phonetic alphabet: alpha, bravo, charlie etc.).
'inure' with 'u' removed is 'IN RE'.
'to' acts as a link.
(Other definitions for in re that I've seen before include "With regard to" , "In the matter of (Lat.)" , "Concerning (L)" .)