Put pen to paper with ceremony (5)
I believe the answer is:
write
'put pen to paper' is the definition.
(I've seen this before)
'with ceremony' is the wordplay.
'with' becomes 'w' (abbreviation).
'ceremony' becomes 'rite' (rite is a kind of ceremony).
'w'+'rite'='WRITE'
(Other definitions for write that I've seen before include "Jot" , "Compose; correspond" , "Inscribe" , "Produce text" , "Compose (a text)" .)