Zero desire to protect the old with limited vision (3-4)
I believe the answer is:
one-eyed
'with limited vision' is the definition.
(I've seen this before)
'zero desire to protect the old' is the wordplay.
'zero' becomes 'O' (O resembles 0).
'desire' becomes 'need' (needing is a kind of desiring).
'to protect' means one lot of letters goes inside another (inserted letters are held or protected).
'the old' becomes 'ye' (resembles a historical spelling of 'the').
'need' placed around 'ye' is 'neeyed'.
'o'+'neeyed'='ONE-EYED'
(Other definitions for one-eyed that I've seen before include "Like the Jack of spades or hearts" , "''In the country of the blind, the . . .-. . . . man is King''" , "Like Cyclops" , "Monocular" .)