Wild thing taking a drop when 30 goes (9)
I believe the answer is:
nightfall
'wild thing taking a drop when 30 goes' is the definition.
I can't judge whether this defines the answer.
'wild thing taking a drop' is the wordplay.
'wild' indicates anagramming the letters.
'taking' means one lot of letters go next to another.
'a drop' becomes 'fall' ('fall' can be a synonym of 'drop'**).
'thing' anagrammed gives 'night'.
'night'+'fall'='NIGHTFALL'
(Other definitions for nightfall that I've seen before include "when the light fails" , "when evenings draw in" , "End of day" , "start of the dark time" , "gloaming" .)