Thus cover one side yard? Hardly (7)
I believe the answer is:
solidly
'hardly' is the definition.
(thesaurus)
'thus cover one side yard?' is the wordplay.
'thus' becomes 'so' (synonyms).
'cover' becomes 'lid' (lid is a kind of cover).
'one side' becomes 'l' (abbreviation for left).
'yard?' becomes 'y' (abbreviation).
'so'+'lid'+'l'+'y'='SOLIDLY'
(Other definitions for solidly that I've seen before include "with substance" , "Reliably, firmly" , "Working in a financially sound way" .)