Relevant language on the fourth of June (7)
I believe the answer is:
germane
'relevant' is the definition.
(germane can mean relevant or pertinent)
'language on the fourth of june' is the wordplay.
'language' becomes 'german' (German is a language).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'the fourth of june' becomes 'e' (4th letter of 'june').
'german'+'e'='GERMANE'
(Other definitions for germane that I've seen before include "Relevant - appropriate" , "apt" , "closely related" , "Relevant to current topic" , "Related to the matter in hand, relevant" .)