A line possibly nice for old people (5)

I believe the answer is:

iceni

I'm a little stuck... Click here to teach me more about this clue!

'old people' is the definition.
(I've seen this before)

'a line possibly nice' is the wordplay.
'a line' becomes 'i' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'possibly' indicates an anagram.
'nice' anagrammed gives 'ceni'.
'i'+'ceni'='ICENI'

'for' is the link.

Can you help me to learn more?

(Other definitions for iceni that I've seen before include "Rebellious tribe" , "Ancient Brits" , "Old warriors" , "Boudica's tribe" , "Ancient British tribe" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.