Work out alone outside entrance to velodrome (5)
I believe the answer is:
solve
'work out' is the definition.
(thesaurus)
'alone outside entrance to velodrome' is the wordplay.
'alone' becomes 'sole' ('sole' can be a synonym of 'alone').
'outside' indicates putting letters inside.
'entrance to' indicates taking the first letters.
The initial letter of 'velodrome' is 'v'.
'sole' enclosing 'v' is 'SOLVE'.
(Other definitions for solve that I've seen before include "Crack clues" , "Find the 3dn to a mystery" , "Explain (a mystery)" , "Find the answer to a mystery" , "Figure out the answer" .)