Question leads to one lucky break, pronto (7)
I believe the answer is:
quickly
'pronto' is the definition.
(thesaurus)
'question leads to one lucky break' is the wordplay.
'leads' suggests taking the first letters.
'to one' becomes 'i' (Roman numeral).
'break' indicates an anagram.
The first letter of 'question' is 'q'.
'i'+'lucky'='ilucky'
'ilucky' with letters rearranged gives 'uickly'.
'q'+'uickly'='QUICKLY'
(Other definitions for quickly that I've seen before include "Mistress of Eastcheap tavern" , "Speedily" , "Rapidly; promptly" , "At speed" .)