Dash from container on craft when unoccupied on river (8)
I believe the answer is:
tincture
'dash from container on craft' is the definition.
'tincture' can be an answer for 'dash' (thesaurus). I am not sure about the 'from container on craft' bit.
'unoccupied on river' is the wordplay.
'unoccupied' becomes 'tinct' (I can't explain this - if you can you should give a lot more credence to this answer).
'on river' becomes 'ure' (I've seen this in other clues).
'tinct'+'ure'='TINCTURE'
'when' acts as a link.
Can you help me to learn more?
(Other definitions for tincture that I've seen before include "(In medicine) an alcoholic solution of a drug" , "Colouring matter" , "Drug dissolved in alcohol; heraldic colour" , "Heraldic colour; medicine" , "Alcohol solution of a drug" .)