Reveal small method (4)
I believe the answer is:
show
'reveal' is the definition.
(I know this)
'small method' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'method' becomes 'how' (I've seen this in another clue).
's'+'how'='SHOW'
(Other definitions for show that I've seen before include "Display cabinet" , "Labour's evidence for starting" , "Portray" , "Point out - parade" , "Musical featuring 'Old Man River'" .)