Regret the loss of flash vase (5)
I believe the answer is:
mourn
'regret the loss' is the definition.
'mourn' can be an answer for 'regret' (I've seen this before). I'm not sure about the 'the loss' bit.
'flash vase' is the wordplay.
'flash' becomes 'mo' (both mean a very short period of time).
'vase' becomes 'urn' (both can mean a container).
'mo'+'urn'='MOURN'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for mourn that I've seen before include "'Miss'" , "Weep for" , "Keen" , "Be sad over loss" , "Express sadness" .)