King wanting new attire, becoming more annoyed (7)
I believe the answer is:
rattier
'more annoyed' is the definition.
(I've seen this before)
'king wanting new attire' is the wordplay.
'king' becomes 'r' (r is abbreviation for rex**).
'wanting' means one lot of letters go next to another.
'new' indicates an anagram.
'attire' anagrammed gives 'attier'.
'r'+'attier'='RATTIER'
'becoming' is the link.
(Other definitions for rattier that I've seen before include "more irritable mood" , "more likely to snap?" , "Not so placid" , "More bad tempered (colloquial)" , "more annoyed" .)