Dead wrong about one being helped (5)
I believe the answer is:
aided
'being helped' is the definition.
(I've seen this before)
'dead wrong about one' is the wordplay.
'wrong' indicates anagramming the letters.
'about' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'dead' is an anagram of 'aded'.
'aded' placed around 'i' is 'AIDED'.
(Other definitions for aided that I've seen before include "'Assisted, helped (5)'" , "not under their own steam?" , "given assistance" .)