A spot in which you'll see navy chaps dressing up (9)
I believe the answer is:
adornment
'dressing up' is the definition.
'a spot in which you'll see navy chaps' is the wordplay.
'spot' becomes 'dot' (I've seen this before).
'in which you'll see' is an insertion indicator.
'navy' becomes 'rn' (abbreviation for Royal Navy).
'chaps' becomes 'men' (I've seen this before).
'rn'+'men'='rnmen'
'dot' placed around 'rnmen' is 'dornment'.
'a'+'dornment'='ADORNMENT'
(Other definitions for adornment that I've seen before include "Decoration" , "decorating" , "Ornamentation" , "Trim" , "Embellishment" .)