Science taken aback after harbour overturned in equatorial region (7)
I believe the answer is:
tropics
'equatorial region' is the definition.
'science taken aback after harbour overturned' is the wordplay.
'science' becomes 'sci' (eg in 'poli sci' for political science).
'taken aback' is a reversal indicator.
'after' means one lot of letters go next to another.
'harbour' becomes 'port' (I've seen this before**).
'overturned' is a reversal indicator.
'sci' back-to-front is 'ics'.
'port' in reverse letter order is 'trop'.
'ics' after 'trop' is 'TROPICS'.
'in' is the link.
(Other definitions for tropics that I've seen before include "Cancer, Capricorn" , "Region either side of equator" , "heated situations" , "hot spot" , "hot spots" .)