Band: T Rex up wearing outrageous gear (6)
I believe the answer is:
garter
'band' is the definition.
(garter is a kind of band)
't rex up wearing outrageous gear' is the wordplay.
'rex' becomes 'r' (common abbreviation e.g. GR=George Rex, King Georg).
'up' is an anagram indicator.
'wearing' is an insertion indicator.
'outrageous' is an anagram indicator (I've seen this in other clues).
't'+'r'='tr'
'tr' anagrammed gives 'rt'.
'gear' anagrammed gives 'gaer'.
'rt' placed inside 'gaer' is 'GARTER'.
(Other definitions for garter that I've seen before include "Stocking supporter" , "Support for a stocking" , "- Belt; - snake; - stitch" , "Band to keep a stocking or sleeve up" , "Band to hold up a stocking" .)