Chap in East London semi (3)
I believe the answer is:
alf
This could be a double definition.
'chap' is the first definition.
(short for Alfred)
'east london semi' is the second definition.
The definition suggests a singular noun which matches the answer.
'in' is the link.
(Other definitions for alf that I've seen before include "See man" , "Mr Garnett" , "Garnett or Ramsey?" , "Ramsey starter" , "Chap" .)