Old hat initially tarnished ceremony (5)
I believe the answer is:
trite
'old hat' is the definition.
(thesaurus)
'initially tarnished ceremony' is the wordplay.
'initially' suggests taking the first letters.
'ceremony' becomes 'rite' (rite is a kind of ceremony).
The first letter of 'tarnished' is 't'.
't'+'rite'='TRITE'
(Other definitions for trite that I've seen before include "Banal, commonplace" , "Commonplace, hackneyed" , "Lyre string" , "(Of an idea) lacking in originality" , "all vigour is gone" .)