Pad page, line one (5)
I believe the answer is:
place
'pad' is the definition.
(I know that pad is a more specific form of the action stuff)
'page line one' is the wordplay.
'page' becomes 'p'.
'line' becomes 'l' (used when specifying particular lines from a poem).
'one' becomes 'ace' (ace has a value of one in some card games).
'p'+'l'+'ace'='PLACE'
(Other definitions for place that I've seen before include "Location; put" , "Spot" , "Locus" , "square?" , "Scene; put" .)