Hymns, perhaps: no good in plea for help (5)
I believe the answer is:
songs
'hymns' is the definition.
(I've seen this before)
'no good in plea for help' is the wordplay.
'no good' becomes 'ng' (abbreviation).
'in' means one lot of letters goes inside another.
'plea for help' becomes 'sos' (Save Our Souls distress message).
'ng' going inside 'sos' is 'SONGS'.
'perhaps' acts as a link.
(Other definitions for songs that I've seen before include "Arias" , "Highish boot support" , "Airs" , "Ballads" , "hymns" .)