Question: are fronted adverbials subordinate clauses?
Answer: Yes. Here is how 'easy' it is to teach 'fronted adverbials' and 'subordinate clauses', according to the descriptions offered by the kind of 'grammar' that is being dished up for Spelling, Punctuation and Grammar tests. ... It is 'subordinate' because it's thought that it 'modifies' or 'qualifies' 'he wore his hat'.