Spots every teenager's nightmare served up in green cabbage (4)
I believe the answer is:
acne
'spots every teenager's nightmare' is the definition.
'acne' can be an answer for 'spots' (skin condition causing spots). I'm unsure of the 'every teenager's nightmare' bit.
'up in green cabbage' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'in' indicates a hidden word.
'enca' is hidden within 'green cabbage'.
'enca' reversed gives 'ACNE'.
'served' is the link.
Can you help me to learn more?
(Other definitions for acne that I've seen before include "Youthful problem" , "Inflammation of glands in skin" , "Adolescent skin disease" , "Skin disorder" , "Spotty coverage" .)