Isaiah's first lament about Biblical character (5)
I believe the answer is:
naomi
'biblical character' is the definition.
(I've seen this before)
'isaiah's first lament about' is the wordplay.
'isaiah's first' becomes 'i' (1st letter of 'isaiah').
'lament' becomes 'moan' (I've seen this in another clue).
'about' is a reversal indicator.
'i'+'moan'='imoan'
'imoan' in reverse letter order is 'NAOMI'.
(Other definitions for naomi that I've seen before include "Girl" , "Ruth's mother-in-law (Bible)" , "woman in the Bible" , "Relative of Ruth" , "Biblical woman" .)