Interferes with the decorations, one might say (7)
I believe the answer is:
meddles
'interferes' is the definition.
(meddling is a kind of interfering)
'decorations one might say' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'me' (a setter might use 'one' to humourously mean 'me') and 'me' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'with the' is the link.
Can you help me to learn more?
(Other definitions for meddles that I've seen before include "Intrude in other people's affairs" , "Intrudes in other people's affairs" , "Interferes, tampers with" .)