Harry Kane describing length: 'It's just over a foot (5)
I believe the answer is:
ankle
''it's just over a foot' is the definition.
(I've seen this in another clue)
'harry kane describing length' is the wordplay.
'harry' indicates an anagram (harry can mean to attack or spoil).
'describing' indicates putting letters inside (describe can mean to form the outline of).
'length' becomes 'l' (abbreviation in geometry).
'kane' anagrammed gives 'anke'.
'anke' enclosing 'l' is 'ANKLE'.
(Other definitions for ankle that I've seen before include "Lower leg joint" , "Narrow part of leg" , "Bone over foot" , "Low joint" , "Location of the talus" .)