Headlong plunge (11)
I believe this clue is a double definition.
'headlong' is the first definition.
(synonyms)
'plunge?' is the second definition.
(thesaurus)
(Other definitions for precipitate that I've seen before include "Suddenly cause - condense and fall (as rain, sleet etc)" , "Bring on" , "rash" , "Cause (a bad event) to happen prematurely" , "Done without careful consideration" .)
(Other definitions for dive that I've seen before include "Seedy bar" , "Plunge into - disreputable club" , "Headlong plunge into water" , "Disreputable establishment" , "Low establishment" .)