Instructs ceramicists to become loco freaks (13)
I believe the answer is:
trainspotters
'become loco freaks' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'instructs ceramicists' is the wordplay.
'instructs' becomes 'trains' (training is a kind of instructing).
'ceramicists' becomes 'potters' ('potter' can be a synonym of 'ceramicist').
'trains'+'potters'='TRAINSPOTTERS'
'to' acts as a link.
Can you help me to learn more?
(Another definition for trainspotters that I've seen is " geeks".)