Plant in ground established grip (8)

I believe the answer is:
interest
'plant in ground established grip' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'plant in ground established' is the wordplay.
I cannot really see how this works, but
'plant' could be 'inter' (to inter in the ground) and 'inter' is located in the answer.
'established' could be 'est' (abbreviation) and 'est' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for interest that I've seen before include "Curiosity or concern, or a financial stake in (8)" , "Deep concern - premium paid for use of money" , "Cost of borrowing" , "attention is shown" , "Money paid on deposit account or loans" .)
