Rudimentary ingredient for a starter of lasagne (9)
I believe the answer is:
elemental
'rudimentary' is the definition.
(thesaurus)
'ingredient for a starter of lasagne' is the wordplay.
'ingredient' becomes 'element' ('element' can be a synonym of 'ingredient'**).
'for' says to put letters next to each other.
'starter of' indicates taking the first letters.
The first letter of 'lasagne' is 'l'.
'element'+'a'+'l'='ELEMENTAL'
(Other definitions for elemental that I've seen before include "key" , "Related to the powers of nature" , "of fire, say" , "Nature spirit" , "being like Mercury?" .)