Tell the Spanish in class (6)
I believe the answer is:
relate
'tell' is the definition.
(as in to tell or relate a story)
'the spanish in class' is the wordplay.
'the spanish' becomes 'el' ('the' in Spanish).
'in' means one lot of letters goes inside another.
'class' becomes 'rate' (class can mean to rank or rate).
'el' put into 'rate' is 'RELATE'.
(Other definitions for relate that I've seen before include "feel empathy" , "Give a report or show a connection" , "Show a connection between (things)" , "Tell - the marriage guidance people" , "Show sympathy" .)