In label on back for all to see: this food is sweet (6)
I believe the answer is:
nougat
'this food is sweet' is the definition.
'nougat' can be an answer for 'food' (nougat is a kind of food). I'm not certain of the rest of the definition.
'in label on back for all' is the wordplay.
'in' is an insertion indicator.
'label' becomes 'tag' (tag is a kind of label).
'back' says the letters should be written in reverse.
'for all' becomes 'U' (Universal film certificate - suitable for all).
'tag'+'on'='tagon'
'tagon' reversed gives 'nogat'.
'nogat' placed around 'u' is 'NOUGAT'.
'to see' acts as a link.
Can you help me to learn more?
(Other definitions for nougat that I've seen before include "Chewy sweet with sugar, honey, nuts etc." , "Sweet made from honey, nuts, sugar, etc" , "Sticky French sweet" , "Chewy confection with nuts, cherries" , "Chewy sweet made of egg-white, nuts and sugar" .)