Even parts of Hamburg reject English endorsement, which is harsh (8)
I believe the answer is:
abrasive
'is harsh' is the definition.
(I've seen this before)
'even parts of hamburg reject english endorsement' is the wordplay.
'even parts of' indicates alternate letters (the letters in even-numbered positions).
'reject' says the letters should be written backwards.
'english' becomes 'E' (abbreviation).
'endorsement' becomes 'visa' (visa is a kind of endorsement).
The alternating letters of 'hamburg' are 'abr'.
'e'+'visa'='evisa'
'evisa' in reverse letter order is 'asive'.
'abr'+'asive'='ABRASIVE'
'which' acts as a link.
(Other definitions for abrasive that I've seen before include "Tending to wear away" , "Harsh - chafing" , "Irritating in manner" , "Rough, irritating" , "rubbing" .)