Extremely coquettish kind of yellow jumper turned up where one goes at night (7,3)
I believe the answer is:
chamber pot
'where one goes at night' is the definition.
(somewhere to urinate or 'go')
'extremely coquettish kind of yellow jumper turned up' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'kind of yellow' becomes 'amber'.
'jumper' becomes 'top'.
'turned up' is a reversal indicator.
'coquettish' with its middle removed is 'ch'.
'top' back-to-front is 'pot'.
'ch'+'amber'+'pot'='CHAMBER POT'
(Other definitions for chamber pot that I've seen before include "Where movement performed" , "Jerry" .)