I’m turning red, including yarns, primarily? (4)
I believe the answer is:
'i'm' is the definition.
I can't tell whether this defines the answer.
'turning red including yarns primarily?' is the wordplay.
'turning' says the letters should be written in reverse.
'including' indicates putting letters inside.
'primarily?' indicates taking the first letters (I've seen 'primarily' mean this).
The first letter of 'yarns' is 'y'.
'red' going around 'y' is 'reyd'.
'reyd' back-to-front is 'DYER'.
(Other definitions for dyer that I've seen before include "Colourer of fabrics", "Fabric stainer", "I change colour", "Fabric colourer", "Increase (in output)".)