Teetotal Tyneside dons exonerate high street trader (3,7)
I believe the answer is:
dry cleaner
'high street trader' is the definition.
(type of trader)
'teetotal tyneside dons exonerate' is the wordplay.
'teetotal' becomes 'dry' (synonyms).
'tyneside' becomes 'NE' (region in North East of England).
'dons' is an insertion indicator (don means to wear or put on).
'exonerate' becomes 'clear' (synonyms).
'ne' going into 'clear' is 'cleaner'.
'dry'+'cleaner'='DRY-CLEANER'
(Other definitions for dry cleaner that I've seen before include "Hero of The Three Musketeers" , "Clothes refresher" , "Who could improve habits" .)