Stitch back the top in one direction only (4)
I believe the answer is:
'one direction only' is the definition.
I can't judge whether this definition defines the answer.
'stitch back the top' is the wordplay.
'stitch' becomes 'sew' (synonyms).
'back' says the letters should be written backwards.
'top' says to take the initial letters (in a down clue, the first letter is top).
The initial letter of 'the' is 't'.
'sew' back-to-front is 'wes'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for west that I've seen before include "English county" , "Dog (from Argyll?)" , "One Direction" , "Mae -, US actress; W" , "The cardinal compass point of 270 degrees" .)