A clever word, really sharp! (5)
I believe the answer is:
acute
'sharp' is the definition.
('acute' can be a synonym of 'sharp')
'a clever' is the wordplay.
'clever' becomes 'cute' (I've seen this before).
'a'+'cute'='ACUTE'
'word really' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for acute that I've seen before include "Incisive" , "Sharp like angle" , "Critical, serious" , "Shrewd; severe" , "Sharp-pointed - keenly perceptive" .)