Painter is drinking gallons with energy to draw (9)
I believe the answer is:
'draw' is the definition.
('draw'->'magnetize' is in my internal thesaurus and 'ize'->'ise')
'painter is drinking gallons with energy' is the wordplay.
'painter' becomes 'manet' (I've seen this before).
'drinking' indicates putting letters inside (inserted letters are consumed or drunk).
'gallons' becomes 'G' (abbreviation).
'with' means one lot of letters go next to another.
'energy' becomes 'e' (physics symbol as in E=mca).
'manetis' placed around 'g' is 'magnetis'.
'to' is the link.
(Another definition for magnetise that I've seen is " create a strong attraction".)