Lead investigator, say, to create mottled design (5,8)
I believe the answer is:
metal detector
'lead investigator say' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'create mottled design' is the wordplay.
'design' is an anagram indicator.
'create'+'mottled'='createmottled'
'createmottled' with letters rearranged gives 'METAL DETECTOR'.
'to' is the link.
Can you help me to learn more?
(Other definitions for metal detector that I've seen before include "Treasure hunter's kit" , "Treasure hunter's tool" , "Treasure-seeking gear" , "Means of finding buried treasure" , "Device used by treasure hunters" .)