Measurement of denims, I altered leg (9)
I believe the answer is:
dimension
'measurement' is the definition.
(dimension is a kind of measurement)
'denims i altered leg' is the wordplay.
'altered' indicates an anagram.
'leg' becomes 'on' (cricket term, fielding positions).
'denims'+'i'='denimsi'
'denimsi' anagrammed gives 'dimensi'.
'dimensi'+'on'='DIMENSION'
'of' is the link.
(Other definitions for dimension that I've seen before include "measure" , "Proportion" , "size" , "Length or breadth, say" .)