Crude sort of weld (4)
I believe the answer is:
lewd
'crude' is the definition.
(thesaurus)
'sort of weld' is the wordplay.
'sort of' is an anagram indicator.
'weld' anagrammed gives 'LEWD'.
(Other definitions for lewd that I've seen before include "Obscene - lustful - sensual" , "Obscene, indecent" , "Weld in lascivious way" , "Indecent, licentious" , "blue" .)