Public transport's turnaround is quick and efficient (5)
I believe the answer is:
smart
'quick and efficient' is the definition.
'public transport's turnaround' is the wordplay.
'public transport's' becomes 'trams'.
'turnaround' shows that the letters should be reversed in order.
'trams' reversed gives 'SMART'.
'is' is the link.
(Other definitions for smart that I've seen before include "Trams (anag.)" , "Elegant and stylish" , "Clever or stylish" , "Trim - sting" , "Bright; sting" .)