Male boarding a red bus excitedly in shorts (8)

'shorts' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

'male boarding a red bus excitedly' is the wordplay.
'male' becomes 'm' (common abbreviation).
'boarding' means one lot of letters goes inside another.
'excitedly' indicates anagramming the letters (letters excited or stimulated into a new form).
'a'+'red'+'bus'='aredbus'
'aredbus' is an anagram of 'berudas'.
'm' put inside 'berudas' is 'BERMUDAS'.

'in' is the link.

Can you help me to learn more?