Endlessly pursue relative in framework (7)
I believe the answer is:
chassis
'framework' is the definition.
(I know that chassis is a type of container)
'endlessly pursue relative in' is the wordplay.
'endlessly' means to remove the last letter.
'pursue' becomes 'chase' (chasing is a kind of pursuing).
'relative in' becomes 'sis' (I can't explain this - if you can you should give a lot more credence to this answer).
'chase' with its final letter removed is 'chas'.
'chas'+'sis'='CHASSIS'
Can you help me to learn more?
(Other definitions for chassis that I've seen before include "Body frame" , "an estate may be built on it" , "Vehicle structure" , "basic structure" , "Car's body" .)