Weight that is misrepresented as something unspecified (7)
I believe the answer is:
whatsit
'something unspecified' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'weight that is misrepresented' is the wordplay.
'weight' becomes 'w' (short for weight).
'misrepresented' indicates anagramming the letters.
'that'+'is'='thatis'
'thatis' is an anagram of 'hatsit'.
'w'+'hatsit'='WHATSIT'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for whatsit that I've seen before include "Something one can't recall" , "Thingummy" , "Thingumajig" , "something indefinable" , "person not to be named" .)