Heavy person best to shift piano (4)
I believe the answer is:
lump
'heavy person' is the definition.
(lump can mean a large person)
'best to shift piano' is the wordplay.
I cannot really understand how this works, but
'piano' could be 'p' (musical abbreviation) and 'p' is found within the answer.
The remaining letters 'lum' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lump that I've seen before include "Small solid mass" , "Irregular mass" , "Plum in a compact shapeless mass" , "Irregularly shaped piece" , "Piece of sugar, coal etc" .)