Simple fashion show's beginning on time (6)
I believe the answer is:
modest
'simple' is the definition.
(synonyms)
'fashion show's beginning on time' is the wordplay.
'fashion' becomes 'mode' (synonyms).
'beginning' indicates taking the first letters.
'on' says to put letters next to each other.
'time' becomes 't' (abbreviation).
The initial letter of 'shows' is 's'.
'mode'+'s'+'t'='MODEST'
(Other definitions for modest that I've seen before include "Demure" , "Humble, not pretentious or showy" , "Not vain, rather shy" , "Prudent" , "Unassuming or decent" .)