Claimed to be working in tens (7)
I believe the answer is:
decimal
'working in tens' is the definition.
'claimed to be' is the wordplay.
'to be' indicates an anagram.
'claimed' anagrammed gives 'DECIMAL'.
(Other definitions for decimal that I've seen before include "fraction" , "A point in maths" , "Claimed (anag) - a point" , "Sort of coinage" , "(System) based on tens" .)