Saint roughly cut narrow piece (5)
I believe the answer is:
strip
'narrow piece' is the definition.
(as in a strip of material or land)
'saint roughly cut' is the wordplay.
'saint' becomes 'st' (abbreviation).
'roughly cut' becomes 'rip' (ripping is a kind of cutting. I am not sure about the 'roughly' bit.).
'st'+'rip'='STRIP'
Can you help me to learn more?
(Other definitions for strip that I've seen before include "Disrobe" , "Undress a long narrow piece" , "US road lined with shops" , "Series of cartoons" , "may be torn off in anger?" .)