Briefly observe treatment that is not easily understood (7)
I believe the answer is:
obscure
'is not easily understood' is the definition.
(I've seen this before)
'briefly observe treatment' is the wordplay.
I cannot quite understand how this works, but
'treatment' could be 'cure' (medical treatment) and 'cure' is found within the answer.
The remaining letters 'obs' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'that' acts as a link.
Can you help me to learn more?
(Other definitions for obscure that I've seen before include "Enigmatic (like Jude?)" , "incomprehensible" , "Recondite, abstruse" , "Unheard-of" , "Like Jude, not well known" .)