Unravel clue — only when verb’s included (5)
I believe the answer is:
solve
'unravel' is the definition.
(I've seen this before)
'clue only when verb's included' is the wordplay.
'clue only' becomes 'sol' (I am not sure about this - if you are sure you should believe this answer much more).
'when' becomes 'e' (I've seen this in other clues).
'verb' becomes 'v' (abbreviation used in dictionaries).
'included' means one lot of letters goes inside another.
'sol'+'e'='sole'
'sole' going around 'v' is 'SOLVE'.
(Other definitions for solve that I've seen before include "Get answer to (a clue)" , "Find the 3dn to a mystery" , "Work out (a problem)" , "Loves (anag) - to find an answer" , "Find the key - work out" .)