Poor diet Tom has skipped (7)
I believe the answer is:
omitted
'skipped' is the definition.
(I've seen this before)
'poor diet tom' is the wordplay.
'poor' is an anagram indicator.
'diet'+'tom'='diettom'
'diettom' is an anagram of 'OMITTED'.
'has' acts as a link.
(Other definitions for omitted that I've seen before include "Cardigan boy" , "Leave undone or leave out" , "Failed" , "Overlooked" , "Hairdressing" .)