Taken in
'taken in' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for seen that I've seen before include "Sighted" , "Met - understood" , "Espied" , "Viewed" , "Witnessed" .)
'taken in' is the definition.
(take in can mean to eat)
'taken in' is the wordplay.
I cannot really see how this works, but
'taken' could be 'ate' (eating is a kind of taking) and 'ate' is found in the answer.
The remaining letters 'en' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for eaten that I've seen before include "Upset" , "having enjoyed dinner?" , "dinners should be" , "This bread is soon forgotten, it's said" , "absorbed in the system" .)