Be located in the heart of Docklands, that is (3)
I believe the answer is:
lie
'be located' is the definition.
(thesaurus)
'heart of docklands that is' is the wordplay.
'heart of' says to take the centre.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
The middle letter of 'docklands' is 'l'.
'l'+'ie'='LIE'
'in the' acts as a link.
(Other definitions for lie that I've seen before include "Piece of fiction" , "Fib - be prone" , "Prevaricate or recline" , "buried" , "Perjure" .)