Having no end in sight (7)
I believe the answer is:
aimless
'having no' is the definition.
I can't tell whether this defines the answer.
'end in sight' is the wordplay.
'end' becomes 'aim' (both can mean a purpose or goal).
'in sight' becomes 'less' (I can't justify this - if you can you should believe this answer much more).
'aim'+'less'='AIMLESS'
Can you help me to learn more?
(Other definitions for aimless that I've seen before include "without sense of purpose" , "Without purpose or plan" , "Lacking a goal" , "lacking direction" , "Without purpose or direction" .)