Subordinate not quickly losing head (5)
I believe the answer is:
lowly
'subordinate' is the definition.
(synonyms)
'not quickly losing head' is the wordplay.
'not quickly' becomes 'slowly' (slow as opposed to quick).
'losing head' means to remove the first letter.
'slowly' with its initial letter removed is 'LOWLY'.
(Other definitions for lowly that I've seen before include "Humble" , "Meek" .)