Short frame cut mostly from a certain metal (7)
I believe the answer is:
stannic
'a certain metal' is the definition.
The definition suggests an adjective which matches the answer.
'short frame cut mostly' is the wordplay.
'short frame' becomes 'stan' (I am not sure about this - if you are sure you should believe this answer much more).
'cut' becomes 'nick' (nick is a kind of cut).
'mostly' means to remove the last letter (most but not all of the word).
'nick' with its last letter taken off is 'nic'.
'stan'+'nic'='STANNIC'
'from' is the link.
Can you help me to learn more?
(Other definitions for stannic that I've seen before include "Relating to one type of tin" , "Of tetravalent tin" , "Of one form of tin" , "containing tin" , "Relating to a form of tin" .)