Undead cruelly holding one without help (7)
I believe the answer is:
unaided
'without help' is the definition.
(I've seen this in another clue)
'undead cruelly holding one' is the wordplay.
'cruelly' is an anagram indicator (I've seen this in other clues).
'holding' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'undead' anagrammed gives 'unaded'.
'unaded' enclosing 'i' is 'UNAIDED'.
(Other definitions for unaided that I've seen before include "Dun aide being without help" , "Done by oneself alone" , "having received zero help" , "Without help or assistance" , "Without extra help" .)