Clean one's uniform -- delayed collecting raincoat (10)
I believe the answer is:
immaculate
'clean' is the definition.
(similar in meaning)
'one's uniform delayed collecting raincoat' is the wordplay.
'one's' becomes 'I'm' ('one is' is a formal way of saying 'I am').
'uniform' becomes 'U' (phonetic alphabet: alpha, bravo, charlie etc.).
'delayed' becomes 'late' (running late).
'collecting' is an insertion indicator.
'raincoat' becomes 'mac' (macintosh is a type of raincoat).
'im'+'u'+'late'='imulate'
'imulate' placed around 'mac' is 'IMMACULATE'.
(Other definitions for immaculate that I've seen before include "Perfect" , "Faultless" , "Dogma that the unborn Virgin Mary was preserved from all original sin" , "conception of a particular religion?" , "Free from flaws" .)