As quick as possible, that is how I am on time (7)
I believe the answer is:
soonest
'as quick as possible' is the definition.
(soon can mean quick)
'that is how i am on time' is the wordplay.
'that is how' becomes 'so' (consequently...).
'i am' becomes 'one's' ('one's' or 'one is' can humorously mean 'I am').
'on' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'so'+'ones'+'t'='SOONEST'
(Other definitions for soonest that I've seen before include "At the earliest time" , "As early as possible" , "First" , "'Least said, ... mended (7)'" , "Most readily" .)