Filled with zeal but still sacked (5)
I believe the answer is:
fired
'still sacked' is the definition.
'fired' can be an answer for 'sacked' (both can mean dismissed from a job). I am not certain of the 'still' bit.
'filled with zeal' is the wordplay.
'filled' becomes 'd' (I can't explain this - if you can you should give a lot more credence to this answer).
'with' means one lot of letters go next to another.
'zeal' becomes 'fire' (I've seen this in another clue).
'd' after 'fire' is 'FIRED'.
'but' is the link.
Can you help me to learn more?
(Other definitions for fired that I've seen before include "Dismissed; set off" , "with P45?" , "Aroused" , "sent up in flames" , "Dismissed or ignited" .)