It could bail one out? (5)
I believe the answer is:
alibi
'it' is the definition.
The definition suggests a singular noun which matches the answer.
'bail one out?' is the wordplay.
'one' becomes 'I' (Roman numeral).
'out?' indicates anagramming the letters (I've seen 'out' mean this (out can mean wrong or inaccurate)).
'bail'+'i'='baili'
'baili' anagrammed gives 'ALIBI'.
'could' acts as a link.
Can you help me to learn more?
(Other definitions for alibi that I've seen before include ""suspect's story"" , "Legal defence proving innocence" , "Proof of being elsewhere at the time of a crime." , "Timely excuse" , "Court evidence showing one was elsewhere" .)