What a day! To start with, this guy made a beastly noise (8)
I believe the answer is:
heehawed
'guy made a beastly noise' is the definition.
I can't judge whether this definition defines the answer.
'what a day to start with' is the wordplay.
'what' becomes 'eh' (sound used to ask 'what?' or 'pardon?').
'day' becomes 'wed' (abbreviation for Wednesday).
'to' means one lot of letters go next to another (I've seen this in other clues).
'start with' becomes 'he' (I can't justify this - if you can you should give a lot more credence to this answer).
'eh'+'a'+'wed'='ehawed'
'ehawed' put after 'he' is 'HEEHAWED'.
'this' acts as a link.
Can you help me to learn more?
(Another definition for heehawed that I've seen is " Made sound like braying donkey".)