Exceedingly lavish taxing across border? (12)
I believe the answer is:
overgenerous
'exceedingly lavish' is the definition.
'overgenerous' can be an answer for 'lavish' (synonyms). I am not certain of the 'exceedingly' bit.
'taxing across border?' is the wordplay.
'taxing' becomes 'onerous' (synonyms).
'across' means one lot of letters goes inside another.
'border?' becomes 'verge' (verging is a kind of bordering).
'onerous' enclosing 'verge' is 'OVERGENEROUS'.
Can you help me to learn more?
(Other definitions for overgenerous that I've seen before include "Giving too much away" , "extremely charitable" , "too liberal?" , "Too bountiful" .)