One may face the wall with this (6)
I believe the answer is:
trowel
'this' is the definition.
The definition suggests a singular noun which matches the answer.
'one may face the wall with' is the wordplay.
I cannot quite see how this works, but
'one' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'with' could be 'w' (abbreviation) and 'w' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for trowel that I've seen before include "Something to help gardener" , "Scoop-shaped tool with short handle" , "Bricklayer's tool" , "Small spade" , "Small garden hand-tool" .)