Suffering if in need, it's endless (10)
I believe the answer is:
indefinite
'endless' is the definition.
(thesaurus)
'suffering if in need it's' is the wordplay.
'suffering' indicates an anagram.
'if'+'in'+'need'+'it'='ifinneedit'
'ifinneedit' anagrammed gives 'INDEFINITE'.
(Other definitions for indefinite that I've seen before include "Vague" , "sort of article" , "Not certain" , "Unsettled" , "rough" .)