Value initially found in exclusive work out (5)
I believe the answer is:
solve
'work out' is the definition.
(thesaurus)
'value initially found in exclusive' is the wordplay.
'initially' indicates taking the first letters.
'found in' means one lot of letters goes inside another.
'exclusive' becomes 'sole' ('sole' can be a synonym of 'exclusive').
The initial letter of 'value' is 'v'.
'v' placed within 'sole' is 'SOLVE'.
(Other definitions for solve that I've seen before include "Crack clues" , "Settle" , "Complete crossword" , "Find the answer to this clue, for instance" , "Voles (anag.)" .)