A clan's system of waterways? (6)
I believe the answer is:
canals
'waterways?' is the definition.
(I know this)
'a clan's system' is the wordplay.
'system' indicates an anagram (another version or system with the same letters).
'a'+'clans'='aclans'
'aclans' is an anagram of 'CANALS'.
'of' is the link.
(Other definitions for canals that I've seen before include "Artificial waterways" , "Artificial water channels" , "Man-made waterways" .)