Wire that's taken by front runner (4)
I believe the answer is:
lead
'wire' is the definition.
(I know that lead is a type of wire)
'taken by front runner' is the wordplay.
'taken by' means one lot of letters go next to another.
'front' becomes 'd' (I am not sure about this - if you are sure you should believe this answer much more).
'runner' becomes 'Lea' (River Lea in South East England).
'd' after 'lea' is 'LEAD'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for lead that I've seen before include "Take a position in front" , "First put down spade, say" , "Show the way; soft metallic element" , "Be in charge of, element" , "Be in charge of; metal" .)