Harmless old copper with nothing is seen in pub with us (9)
I believe the answer is:
innocuous
'harmless' is the definition.
(synonyms)
'nothing is seen in pub with us' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'is seen' becomes 'cuo' (I can't justify this - if you can you should believe this answer much more).
'in' means one lot of letters goes inside another.
'pub' becomes 'inn' (an inn is a type of pub).
'with' says to put letters next to each other.
'o'+'cuo'='ocuo'
'inn'+'us'='innus'
'ocuo' put within 'innus' is 'INNOCUOUS'.
'old copper with' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for innocuous that I've seen before include "Harmless" , "Not harmful or offensive" .)