Greek character, sailor, about to cross river — the quickest route? (3,3)
I believe the answer is:
rat run
'the quickest route?' is the definition.
(term for a road which acts as a shortcut)
'greek character sailor about to cross river' is the wordplay.
'greek character' becomes 'nu' (letter from the Greek alphabet).
'sailor' becomes 'tar' (tar is a kind of sailor**).
'about' shows that the letters should be reversed in order.
'to cross' is an insertion indicator.
'river' becomes 'r'.
'nu'+'tar'='nutar'
'nutar' written backwards gives 'ratun'.
'ratun' enclosing 'r' is 'RAT RUN'.
(Other definitions for rat run that I've seen before include "'Busy side-road during rush hour (3,3)'" , "Side street much used by cars in rush hours" , "Backstreet heavily used by drivers" , "Busy rush-hour side road" , "Heavily used back street" .)