Hospital direction indicator in London borough (6)
I believe the answer is:
harrow
'london borough' is the definition.
(I know that Harrow is London borough)
'hospital direction indicator' is the wordplay.
'hospital' becomes 'H' (abbreviation for hospital on maps).
'direction indicator' becomes 'arrow' (I've seen this in another clue).
'h'+'arrow'='HARROW'
'in' is the link.
(Other definitions for harrow that I've seen before include "Soil cultivator - English public school" , "Agricultural frame for breaking up soil" , "It breaks up clods and covers seeds" , "Spiked frame for breaking and levelling soil" , "Soil-breaking implement" .)