In darts, it’s where to toe the line (4)
I believe the answer is:
oche
'line' is the definition.
(I've seen this before)
'in darts it's' is the wordplay.
'in darts' becomes 'och' (I can't justify this - if you can you should give a lot more credence to this answer).
'it' becomes 'e' ('e' can mean 'electronic' which is similar to 'IT').
'och'+'e'='OCHE'
'where to toe the' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for oche that I've seen before include "Line at which darts player stands to throw" , "Line of 25 [ARROEWS]" , "Line behind which an 11 player throws" , "Dart-playing line" , "Line behind which darts players stand" .)