Personnel concealing anger for employer (5)
I believe the answer is:
hirer
'employer' is the definition.
(hirer is a kind of employer)
'personnel concealing anger' is the wordplay.
'personnel' becomes 'hr' (Human Resources).
'concealing' indicates putting letters inside.
'anger' becomes 'ire' (synonyms).
'hr' placed around 'ire' is 'HIRER'.
'for' is the link.
(Other definitions for hirer that I've seen before include "One who lets out" , "Renter" , "He purchases tempory use of something" , "Person who takes on workers" , "One taking on workers" .)