Joint action — worm turning in wood (8)
I believe the answer is:
teamwork
'joint action' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's a link between them I don't understand?
'worm turning in wood' is the wordplay.
'turning' indicates anagramming the letters.
'in' means one lot of letters goes inside another.
'wood' becomes 'teak' (type of timber).
'worm' is an anagram of 'mwor'.
'mwor' put inside 'teak' is 'TEAMWORK'.
Can you help me to learn more?
(Other definitions for teamwork that I've seen before include "Concert" , "joint operating" , "It demands action by several folk" , "Co-ordination" , "Effective action of a group" .)