Type of grass father's maintaining foremost in meadow (6)
I believe the answer is:
pampas
'type of grass' is the definition.
(pampas grass is a flowering plant)
'father's maintaining foremost in meadow' is the wordplay.
'father's' becomes 'papa's' (papa can mean one's father).
'maintaining' means one lot of letters goes inside another (inserted letters are held or maintained).
'foremost in' suggests taking the first letters.
The first letter of 'meadow' is 'm'.
'papas' placed around 'm' is 'PAMPAS'.
(Other definitions for pampas that I've seen before include "Prairies (with grass)" , "Treeless plain(s)" , "South American grassland" , "Argentinian plains" , "Great plains of Argentina" .)