Disregard 2D? I can’t, ultimately (4)
I believe the answer is:
omit
'disregard' is the definition.
(I've seen this in another clue)
'2d? i can't ultimately' is the wordplay.
'md?' becomes 'om' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ultimately' suggests the final letters.
The final letter of 'cant' is 't'.
'om'+'i'+'t'='OMIT'
Can you help me to learn more?
(Other definitions for omit that I've seen before include "Leave out or forget" , "Fail to mention" , "Fail (to do something)" , "Take out" , "Neglect to include" .)