Mountaineer clubs get ready for action (7)
I believe the answer is:
climber
'mountaineer' is the definition.
(I know that climber is a type of mountaineer)
'clubs get ready for action' is the wordplay.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'get ready for action' becomes 'limber' (as in limbering up).
'c'+'limber'='CLIMBER'
(Other definitions for climber that I've seen before include "Mountaineer" , "Bonnington" , "in the garden" , "Edward Whymper, for example" , "Plant such as ivy" .)