Unqualified to use lab otherwise (8)
I believe the answer is:
absolute
'unqualified' is the definition.
('absolute' can be similar in meaning to 'unqualified')
'to use lab otherwise' is the wordplay.
'otherwise' is an anagram indicator.
'to'+'use'+'lab'='touselab'
'touselab' is an anagram of 'ABSOLUTE'.
(Other definitions for absolute that I've seen before include "Rival" , "sure" , "Despotic" , "Total; unqualified" , "Unlimited; not relative" .)