Dead reserved (5)
I believe the answer is:
stiff
I believe this clue is a double definition.
'dead' is the first definition.
(thesaurus)
'reserved' is the second definition.
(thesaurus)
(Other definitions for stiff that I've seen before include "Not easily bent" , "cheat" , "Starched, rigid" , "Inflexible" , "18 [HARD]" .)