Only a silver lining is too little (6)
I believe the answer is:
meagre
'too little' is the definition.
'meagre' can be an answer for 'little' (I've seen this before). I'm not sure about the 'too' bit.
'only a silver lining' is the wordplay.
'only' becomes 'mere' (I've seen this before).
'a silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'lining' indicates putting letters inside.
'mere' going around 'ag' is 'MEAGRE'.
'is' is the link.
Can you help me to learn more?
(Other definitions for meagre that I've seen before include "Inadequate, scanty" , "Scanty, not plentiful" , "Scanty in amount - puts me in rage" , "Thin, lacking quality" , "Thin -- inadequate" .)