Flier for whom half a pint's plenty (5)
I believe the answer is:
pilot
'flier' is the definition.
(I know that pilot is a type of aircraft pilot)
'half a pint's plenty' is the wordplay.
'half a' indicates taking half.
'plenty' becomes 'lot' (I can't explain this - if you can you should give a lot more credence to this answer).
'pint' with half the letters taken is 'pi'.
'pi'+'lot'='PILOT'
'for whom' acts as a link.
Can you help me to learn more?
(Other definitions for pilot that I've seen before include "Guide - flier" , "trial episode" , "may be up in the clouds" , "Small flame that ignites a gas boiler" , "Captain of plane or boat" .)