Five laid wrong: acceptable? (5)
I believe the answer is:
valid
'acceptable?' is the definition.
(I've seen this in another clue)
'five laid wrong' is the wordplay.
'five' becomes 'v' (Roman numeral).
'wrong' indicates an anagram.
'laid' is an anagram of 'alid'.
'v'+'alid'='VALID'
(Other definitions for valid that I've seen before include "Well-founded" , "still in force" , "Legally in force" , "Legally good" , "Reasonable" .)