pound - kilogram, acre - ?

HECTARE
List of words for the clue pound - kilogram, acre - ? from the crossword:
YARD MILE METRE KILOMETRE INCH GALLON CENTEMETRE UNIT KILO LITRE ROO LITER EZRA ROOD TONNES MASS EEYORE ROODS QUID
WordClue
ACREkilogram - pound, hectare - ?
INCHkilogram - pound, centemetre - ?
MASSsecond - time, kilogram - ?
MILEkilogram - pound, kilometre - ?
TIMEkilogram - mass, second - ?
UNITkilogram or hertz
YARDkilogram - pound, metre - ?
LITREpound - kilogram, gallon - ?
METERmass - kilogram, distance - ?
METREpound - kilogram, yard - ?
POUNDhectare - acre, kilogram - ?
GALLONkilogram - pound, litre - ?
SECONDmass - kilogram, time - ?
DISTANCEkilogram - mass, meter - ?
KILOGRAMyard - metre, pound - ?
STERLINGpound
KILOMETREpound - kilogram, mile - ?
CENTEMETREpound - kilogram, inch - ?
STERLINGpound
LITREpound - kilogram, gallon - ?