Being sloppy makes the French cross (3)
I believe the answer is:
lax
'being sloppy' is the definition.
(thesaurus)
'the french cross' is the wordplay.
'the french' becomes 'la'.
'cross' becomes 'x' (**).
'la'+'x'='LAX'
'makes' is the link.
(Other definitions for lax that I've seen before include "Not strict enough" , "Casual" , "Insufficiently strict" , "Not sufficiently careful" , "Slapdash" .)