Being soppy, drove one crazy (11)
I believe the answer is:
sentimental
'being soppy' is the definition.
(thesaurus)
'drove one crazy' is the wordplay.
'drove' becomes 'sent' (I've seen this in other clues).
'one' becomes 'i' (Roman numeral).
'crazy' becomes 'mental' (I've seen this before).
'sent'+'i'+'mental'='SENTIMENTAL'
(Other definitions for sentimental that I've seen before include "Evoking tender emotions" , "Appealing to emotion rather than actuality" , "With tender, nostalgic or sad feelings" , "Moved by fond memories of the past" , "pathetic" .)