Posh but dry setting for eastern liner (6)
I believe the answer is:
dressy
'posh' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'dry setting for eastern liner' is the wordplay.
'setting for' means one lot of letters goes inside another (inserted letters are set inside others).
'eastern liner' becomes 'ess' (I can't explain this - if you can you should give a lot more credence to this answer).
'dry' enclosing 'ess' is 'DRESSY'.
'but' acts as a link.
Can you help me to learn more?
(Other definitions for dressy that I've seen before include "Wearing stylish clothes, elegant (6)" , "Formal or elegant" , "'Stylish, smart (6)'" , "Sartorially elegant" , "swish" .)