One in ten men working to become famous (7)
I believe the answer is:
eminent
'famous' is the definition.
(thesaurus)
'one in ten men working' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'working' indicates an anagram.
'ten'+'men'='tenmen'
'tenmen' anagrammed gives 'emnent'.
'i' going inside 'emnent' is 'EMINENT'.
'to become' is the link.
(Other definitions for eminent that I've seen before include "Famous and admired" , "Outstanding or distinguished (7)" , "Important" , "High" , "Distinguished, prominent" .)