Clock face used by lad climbing around India (4)
I believe the answer is:
dial
'clock face' is the definition.
(I've seen this in another clue)
'lad climbing around india' is the wordplay.
'climbing' says the letters should be written in reverse (in a down clue, letters climb up).
'around' indicates putting letters inside.
'india' becomes 'i' (phonetic alphabet: alpha, bravo, charlie etc.).
'lad' in reverse letter order is 'dal'.
'dal' enclosing 'i' is 'DIAL'.
'used by' is the link.
(Other definitions for dial that I've seen before include "Calibrated disc etc" , "Laid up like clock-face" , "Face with numbers" , "feature of old phone?" , "Ring the clock-face" .)