A line possibly nice for old people (5)
I believe the answer is:
iceni
'old people' is the definition.
(ancient tribe of Britain)
'a line possibly nice' is the wordplay.
I cannot really see how this works, but
an anagram of 'nice' is 'icen' which is within the answer.
A single letter 'i' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'for' acts as a 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" .)