Oscar, writing half-heartedly, finds opportunity (7)
I believe the answer is:
opening
'opportunity' is the definition.
(I know that opening is a type of opportunity)
'oscar writing half-heartedly' is the wordplay.
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'writing half-heartedly' becomes 'pening' (I can't justify this - if you can you should give a lot more credence to this answer).
'o'+'pening'='OPENING'
'finds' acts as a link.
Can you help me to learn more?
(Other definitions for opening that I've seen before include "- - time (pub)" , "Aperture or opportunity" , "Window of opportunity" , "Beginning, available job" , "Orifice; opportunity" .)