Language of bridge is hard (7)
I believe the answer is:
spanish
'language' is the definition.
(I know that Spanish is a type of Latinian language)
'bridge is hard' is the wordplay.
'bridge' becomes 'span' (synonyms).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'span'+'is'+'h'='SPANISH'
'of' is the link.
(Other definitions for spanish that I've seen before include "Language of much of Central America" , "Has spin (anag)" , "From Valencia or Malaga?" , "His pans are from Barcelona, say" , "The nationality has his naps" .)