For example, marks up uninviting meal (6)
I believe the answer is:
stodge
'uninviting meal' is the definition.
'stodge' can be an answer for 'meal' (I have seen 'Heavy meal ' mean 'stodge' so perhaps 'meal' could also mean 'stodge'). I am not sure about the 'uninviting' bit.
'for example marks up' is the wordplay.
'for example' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'marks' becomes 'dots' (dotting is a kind of marking).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'eg'+'dots'='egdots'
'egdots' back-to-front is 'STODGE'.
Can you help me to learn more?
(Other definitions for stodge that I've seen before include "Indigestible or dull food" , "Heavy food (colloq.)" , "Set dog (anag)" , "Heavy filling food" , "Heavy and indigestible food" .)