Clumsily saw hairline crack at the edges (4)
I believe the answer is:
hack
'clumsily saw' is the definition.
'hack' can be an answer for 'saw' (thesaurus). I am not sure about the 'clumsily' bit.
'hairline crack at the edges' is the wordplay.
'hairline' becomes 'ha' (I can't explain this - if you can you should give a lot more credence to this answer).
'at the edges' means to remove the middle letters.
'crack' with its middle taken out is 'ck'.
'ha'+'ck'='HACK'
Can you help me to learn more?
(Other definitions for hack that I've seen before include "Drudge, inferior writer" , "Chop - reporter" , "Ride" , "Chop roughly - mediocre journalist" , "Chop at hired horse?" .)