Perhaps: (untested in absence of reproducible example)
eff2 <- effects$tables$x1[['2']]
eff2[ order(eff2) ][1:5]
Or perhaps (still untested in conitnued absence of example)
efftabls <- sapply(eff2, '[', 2)
head( efftabls[order(efftabls)], 5) # 5 used to be the number requested