Eucalyptus bush, one seen in trendy pub (8)

'eucalyptus' is the definition.
(I have seen 'Australian eucalyptus ' mean 'coolibar' so perhaps 'eucalyptus' could also mean 'coolibar')

'one seen in trendy pub' is the wordplay.
'one' becomes 'i' (Roman numeral).
'seen in' indicates putting letters inside.
'trendy' becomes 'cool' (I can't justify this - if you can you should give a lot more credence to this answer).
'pub' becomes 'bar' (both are drinking establishments).
'cool'+'bar'='coolbar'
'i' placed into 'coolbar' is 'COOLIBAR'.

'bush' acts as a link.
This may not be right. It may belong to another bit of the clue.

Can you help me to learn more?