What potter did seeing sign of decay outwardly exposed (7)
I believe the answer is:
moulded
'what potter did' is the definition.
(eg a potter might mould using clay)
'sign of decay outwardly exposed' is the wordplay.
'sign of decay' becomes 'mould' (eg mould shows decay on fruit).
'outwardly' says to hollow out the word (remove centre letters) (only the outermost letters are used).
'exposed' with its middle taken out is 'ed'.
'mould'+'ed'='MOULDED'
'seeing' is the link.
(Other definitions for moulded that I've seen before include "Formed; shaped" , "Determined" .)