Was unhappy parking in the rain (4)
I believe the answer is:
wept
'was unhappy' is the definition.
(I've seen this before)
'parking in the rain' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'in the' means one lot of letters goes inside another.
'rain' becomes 'wet' (I've seen this in other clues).
'p' inserted into 'wet' is 'WEPT'.
(Other definitions for wept that I've seen before include ""Jesus __" (shortest verse in the King James Bible)" , "Shed tears of grief" , "Sobbed heavily" , "lamented" , "Was unhappy" .)