Some yellow length of cloth (3)
I believe the answer is:
ell
'length of cloth' is the definition.
(historical fabric measurement)
'some yellow' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ELL' is hidden within 'yellow'.
(Other definitions for ell that I've seen before include "Former textile measure" , "Former measure of length" , "Old 45-inch measure" , "Once, forty-five inches" , "Old unit of length" .)