Work out alone, about five (5)
I believe the answer is:
solve
'work out' is the definition.
(thesaurus)
'alone about five' is the wordplay.
'alone' becomes 'sole' ('sole' can be a synonym of 'alone').
'about' means one lot of letters goes inside another.
'five' becomes 'v' (roman numeral).
'sole' going around 'v' is 'SOLVE'.
(Other definitions for solve that I've seen before include "Find the answer or explanation" , "Find the solution to puzzle or problem" , "Clear up a mystery" , "Figure out the answer" , "Find the answer to a mystery" .)