Many may be left somewhere in South Holland (5)
I believe the answer is:
delft
'somewhere in south holland' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'many may be left' is the wordplay.
'many' becomes 'D' (Roman numeral for 500).
'may be' indicates anagramming the letters.
'left' is an anagram of 'elft'.
'd'+'elft'='DELFT'
Can you help me to learn more?
(Other definitions for delft that I've seen before include "crockery pieces" , "Netherlands town famed for pottery" , "Dutch blue/white glazed earthenware" , "City in the Netherlands" , "Style of earthenware" .)