Spontaneously films port of Maputo at intervals, adding Uganda's capital (9)
I believe the answer is:
impromptu
'spontaneously' is the definition.
(synonyms)
'films port of maputo at intervals adding uganda's capital' is the wordplay.
'at intervals' indicates alternate letters (letters are taken at regular intervals).
'adding' is a charade indicator (letters next to each other).
'capital' suggests taking the first letters.
The first letter of 'ugandas' is 'u'.
'films'+'port'+'of'+'maputo'='filmsportofmaputo'
The alternating letters of 'filmsportofmaputo' are 'imprompt'.
'imprompt'+'u'='IMPROMPTU'
(Other definitions for impromptu that I've seen before include "Unscripted" , "With little or no preparation or forethought" , "Without pre-planning" , "Unplanned; instrumental piece" , "Piano piece" .)