Basic things, arguably lousy and tough (5-6)
I believe the answer is:
nitty-gritty
'basic things' is the definition.
'arguably lousy and tough' is the wordplay.
'arguably lousy' becomes 'nitty' (nits are the eggs of headlice).
'and' is a charade indicator (letters next to each other).
'tough' becomes 'gritty'.
'nitty'+'gritty'='NITTY-GRITTY'
(Other definitions for nitty-gritty that I've seen before include "Brass tacks" , "Essential details of a matter" , "Most important details (of a matter)" , "Essential aspects" , "Essence" .)