Careless fellow caught out by chance (9)
I believe the answer is:
haphazard
'careless' is the definition.
(similar in meaning)
'by chance' is the wordplay.
'by' becomes 'hap' (I can't explain this - if you can you should give a lot more credence to this answer).
'chance' becomes 'hazard' (synonyms).
'hap'+'hazard'='HAPHAZARD'
'fellow caught out' 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 haphazard that I've seen before include "Lacking any obvious organisation" , "Slapdash, slipshod" , "Careless or random" , "Disorganised, random" , "Lacking order" .)