Little may be seen through it (10)
I believe the answer is:
microscope
'seen through it' is the definition.
I can't tell whether this defines the answer.
'little may' is the wordplay.
'little' becomes 'micro' (similar in meaning).
'may' becomes 'scope' (I can't explain this - if you can you should give a lot more credence to this answer).
'micro'+'scope'='MICROSCOPE'
'be' is the link.
Can you help me to learn more?
(Other definitions for microscope that I've seen before include "Tiny organisms viewer" , "Device for seeing very small objects" , "Magnifying device" , "Optical instrument" , "Optical magnifier" .)