Gain knowledge, seen at last, before not initially clear (5)
I believe the answer is:
learn
'gain knowledge' is the definition.
(synonyms)
'at last before not initially clear' is the wordplay.
'at' means one lot of letters go next to another.
'last before' becomes 'n' (I can't justify this - if you can you should give a lot more credence to this answer).
'not initially' means to remove the first letter.
'clear' with its initial letter taken away is 'lear'.
'n' after 'lear' is 'LEARN'.
'seen' is the link.
Can you help me to learn more?
(Other definitions for learn that I've seen before include "Absorb as knowledge, from book or experience" , "Hear - memorise" , "Gain knowledge or skill" , "Take in" , "Renal (anag)" .)