Dad has endless frolic in wood (6)
I believe the answer is:
poplar
'wood' is the definition.
(poplar is a kind of wood)
'dad has endless frolic' is the wordplay.
'dad' becomes 'pop' ('pop' can be a synonym of 'dad').
'has' means one lot of letters go next to another.
'endless' means to remove the last letter.
'frolic' becomes 'lark' ('lark' can be a synonym of 'frolic').
'lark' with its last letter removed is 'lar'.
'pop'+'lar'='POPLAR'
'in' is the link.
(Other definitions for poplar that I've seen before include "Tall fast-growing tree; East London area" , "Tree of willow family" , "Tall tree of north temperate regions" , "part of our capital" , "Slender tree with quivering leaves" .)