Clear answers billions initially work out (7)
I believe the answer is:
absolve
'clear' is the definition.
(thesaurus)
'answers billions initially work out' is the wordplay.
'initially' suggests taking the first letters.
'work out' becomes 'solve' (I've seen this before**).
The first letters of 'answers billions' is 'ab'.
'ab'+'solve'='ABSOLVE'
(Other definitions for absolve that I've seen before include "Forgive sins" , "Grant remission of sins" , "Declare (someone) guilt-free" , "Let off the hook" , "Declare (someone) blameless" .)