What was tense man on assistant? Busted essentially! (3,4)

'assistant? busted essentially' is the definition.
I can't tell whether this definition defines the answer.

'what was tense man on' is the wordplay.
'what was' becomes 'past' (I've seen this in another clue).
'tense' becomes 't' (grammatical abbreviation).
'man' becomes 'he' (he refers to a man).
'on' says to put letters next to each other.
't'+'he'='the'
'past' put after 'the' is 'THE PAST'.

Can you help me to learn more?