Talk a lot in picking a side (3)
I believe the answer is:
gas
'talk a lot' is the definition.
(gas can mean to talk at length)
'in picking a side' is the wordplay.
'in' indicates the answer is hidden within the clue.
'GAS' is hidden within 'picking a side'.
(Other definitions for gas that I've seen before include "may fill American car" , "Petrol (USA)" , "Form of fossil fuel" , "Eg, nitrogen" , "that may quickly be stepped on" .)