Fold in collars of turtleneck (4)
I believe the answer is:
tuck
'fold' is the definition.
(I know that tuck is a type of plait)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for tuck that I've seen before include "Schoolboy grub like sweets and cakes" , "Fold - friar!" , "Friar of Sherwood" , "Pleat in garment" , "School food" .)