Consider adding water to a half of beer (6)
I believe the answer is:
ponder
'consider' is the definition.
(I know that consider is a more specific form of ponder)
'adding water to a half of beer' is the wordplay.
I cannot really see how this works, but
'water' could be 'pond' (pond is a kind of water) and 'pond' is found within the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ponder that I've seen before include "Meditate - deliberate" , "Muse" , "Consider deeply" , "Meditate, think deeply" , "4 down" .)