Don’t include it after starting on multi-vitamins (4)
I believe the answer is:
omit
'don't include' is the definition.
(I've seen this in another clue)
'it after starting on multi-vitamins' is the wordplay.
'after' means one lot of letters go next to another.
'starting' indicates taking the first letters.
'multi-vitamins' becomes 'm' (this could be a standard abbreviation which I don't know about).
The first letter of 'on' is 'o'.
'o'+'m'='om'
'it' after 'om' is 'OMIT'.
Can you help me to learn more?
(Other definitions for omit that I've seen before include "Drop" , "Leave out or exclude" , "Fail to mention" , "Fail (to do something)" , "Disregard" .)