Fifty set out perhaps to find means of escape (7)
I believe the answer is:
outlets
'means of escape' is the definition.
Although both the answer and definition are plural nouns, I don't see how one could define the other.
'fifty set out perhaps' is the wordplay.
'fifty' becomes 'L' (Roman numeral).
'perhaps' indicates an anagram.
'l'+'set'+'out'='lsetout'
'lsetout' is an anagram of 'OUTLETS'.
'to find' acts as a link.
Can you help me to learn more?
(Other definitions for outlets that I've seen before include "Retail shops" , "Points" , "Place for retailing goods" , "Vents" , "Discharge pipes; shops" .)