Identifier I put on foot of triple jumper (6)
I believe the answer is:
cardie
'jumper' is the definition.
'identifier i put on foot of triple' is the wordplay.
'identifier' becomes 'card'.
'put on' means one lot of letters go next to another.
'foot of' suggests the final letters.
The final letter of 'triple' is 'e'.
'card'+'i'+'e'='CARDIE'
(Other definitions for cardie that I've seen before include "Jumper (colloq.)" , "Knitted jacket that buttons up the front (abbr)" .)