Unfortunately let rip a number of times (6)
I believe the answer is:
triple
'a number of times' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'unfortunately let rip' is the wordplay.
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'let'+'rip'='letrip'
'letrip' is an anagram of 'TRIPLE'.
Can you help me to learn more?
(Other definitions for triple that I've seen before include "In three parts" , "Increase threefold" , "Multiply by three" , "make much longer" , "Consisting of three" .)