Inability to feel popular, with one imprisoned by court decision (11)
I believe the answer is:
insentience
'inability to feel' is the definition.
I can't tell whether this defines the answer.
'popular with one imprisoned by court decision' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'with' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'imprisoned by' is an insertion indicator.
'court decision' becomes 'sentence' (I can't explain this - if you can you should believe this answer much more).
'i' put within 'sentence' is 'sentience'.
'in'+'sentience'='INSENTIENCE'
Can you help me to learn more?
(Another definition for insentience that I've seen is " lack of "feel"".)