French are imprisoning the old observers (4)
I believe the answer is:
eyes
'observers' is the definition.
Although both the answer and definition are plural nouns, I cannot see how they can define each other.
'french are imprisoning the old' is the wordplay.
'french are' becomes 'es' ('are' in French).
'imprisoning' indicates putting letters inside.
'the old' becomes 'ye' (resembles a historical spelling of 'the').
'es' going around 'ye' is 'EYES'.
Can you help me to learn more?
(Other definitions for eyes that I've seen before include "They see and" , "Parts of needles" , "Storm centres" , "''Drink to me only with thine ...'' (Johnson)" , "Regards -- features of a potato" .)