Poet with high honour in extremely leafy part of Italy (8)
I believe the answer is:
lombardy
'part of italy' is the definition.
(I know this)
'poet with high honour in extremely leafy' is the wordplay.
'poet' becomes 'bard' (bard is a kind of poet).
'with' means one lot of letters go next to another.
'high honour' becomes 'OM' (Order of Merit).
'in' is an insertion indicator.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'leafy' with its centre removed is 'ly'.
'bard' put after 'om' is 'ombard'.
'ombard' put into 'ly' is 'LOMBARDY'.
(Other definitions for lombardy that I've seen before include "Region of north Italy bordering Switzerland" , "Great Italian plain between Alps and Po" , "Region of northern Italy" , "Region around Milan" , "Italian region between Alps and the river Po" .)