Unusual stiff arguments (5)
I believe the answer is:
tiffs
'arguments' is the definition.
(I know that bicker is a type of arguments)
'unusual stiff' is the wordplay.
'unusual' indicates an anagram.
'stiff' anagrammed gives 'TIFFS'.
(Other definitions for tiffs that I've seen before include "Small quarrels" , "Petty quarrels" , "Huffs; squabbles" , "Arguments" , "Spats" .)