Notice a port developed into something useful (7)
I believe the answer is:
adaptor
'something useful' is the definition.
I can't judge whether this defines the answer.
'notice a port developed' is the wordplay.
'notice' becomes 'ad' (short for advert).
'developed' indicates an anagram.
'port' anagrammed gives 'ptor'.
'ad'+'a'+'ptor'='ADAPTOR'
'into' acts as a link.
Can you help me to learn more?
(Other definitions for adaptor that I've seen before include "Kind of electric plug" , "Connector (O, not E)" , "It enables fit" , "Connector for differing plug types" , "Device for connecting multiple plugs (O, not E)" .)