In the grass, very quiet and contented (5)
I believe the answer is:
happy
'contented' is the definition.
(I've seen this before)
'in the grass very quiet' is the wordplay.
'in the' means one lot of letters goes inside another.
'grass' becomes 'hay' (I have seen 'Mown grass ' mean 'hay' so perhaps 'grass' could also mean 'hay').
'very quiet' becomes 'pp' (**).
'hay' placed around 'pp' is 'HAPPY'.
'and' acts as a link.
(Other definitions for happy that I've seen before include "Blissful" , "Delighted" , "A not so low" , "Pleased; fortunate" , "Well-pleased" .)