It won't be found in the pack (4,4)
I believe the answer is:
lone wolf
'it won't be' is the definition.
The definition suggests a singular noun which matches the answer.
'in the pack' is the wordplay.
'in the' becomes 'lone' (I am not sure about this - if you are sure you should believe this answer much more).
'pack' becomes 'wolf pack' (wolf pack is a kind of pack).
'lone'+'wolf'='LONE-WOLF'
'found' is the link.
Can you help me to learn more?
(Other definitions for lone wolf that I've seen before include "one preferring his own company" , "Independent operator" , "He likes to operate by himself" , "One avoids the company the others" , "independent type" .)