The most common and most likely answer to this crossword clue is the 6 plus 4 letter word SQUARE EYES
I've seen this crossword clue in The Guardian
S
Q
U
A
R
E
E
Y
E
S
Buddy explains!
The straight part
We know that "this after watching TV for too long" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case this after watching tv for too long = square eyes.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.