Like patterned cloth, all square, you had once (3-4)
I believe the answer is:
tie-dyed
'like patterned cloth all square you had once' is the definition.
I can't judge whether this definition defines the answer.
'all square you had once' is the wordplay.
'all square' becomes 'tied' (I've seen this in another clue).
'you' becomes 'ye' (historical version of 'you').
'had once' becomes 'd' (in contractions e.g. 'I'd', 'you'd' etc. I am not sure about the 'once' bit.).
'tied'+'ye'+'d'='TIE-DYED'
Can you help me to learn more?
(Other definitions for tie-dyed that I've seen before include "Coloured using a particular technique" , "Coloured unevenly" , "Like some patchily coloured fabrics" , "Like some fabric patterns" , "Like some parti-coloured fabrics" .)