Ill-tempered elk bites Republican (6)
I believe the answer is:
morose
'ill-tempered' is the definition.
(I've seen this before)
'elk bites republican' is the wordplay.
'elk' becomes 'moose' (synonyms).
'bites' indicates putting letters inside.
'republican' becomes 'R' (political abbreviation).
'moose' placed around 'r' is 'MOROSE'.
(Other definitions for morose that I've seen before include "grouchy" , "Sad" , "in a grumpy mood" , "Rarely" , "Melancholy" .)