Dismissed Mr Flintstone for getting out of line (5)
I believe the answer is:
fired
'dismissed mr flintstone' is the definition.
'fired' can be an answer for 'dismissed' ('fire' can be a synonym of 'dismiss'). I'm not sure about the 'mr flintstone' bit.
'getting out of line' is the wordplay.
'getting out of' becomes 'fi' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'line' becomes 'red line' (red line is a kind of line).
'fi'+'red'='FIRED'
'for' is the link.
Can you help me to learn more?
(Other definitions for fired that I've seen before include "with P45?" , "Encouraged" , "Dismissed or ignited" , "Set ablaze" , "got rid of" .)