It’s reasonably seen, you feel (5)
I believe the answer is:
sense
'feel' is the definition.
(I've seen this before)
'it's reasonably seen you' is the wordplay.
I cannot quite see how this works, but
an anagram of 'seen' is 'ense' which is within the answer.
A single letter 's' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sense that I've seen before include "Could be hearing" , "definition" , "Feel intuitively" , "Perceptual faculty" , "Get an impression" .)