Sail south, having a kip at first in Greater London town (9)
I believe the answer is:
spinnaker
'sail' is the definition.
(I know that spinnaker is a type of headsail)
'south having a kip at first in greater london town' is the wordplay.
'south' becomes 's' (abbreviation).
'having' is a charade indicator (letters next to each other).
'at first' suggests taking the first letters.
'in' indicates putting letters inside.
'greater london town' becomes 'Pinner' (Pinner is a London suburb).
The initial letter of 'kip' is 'k'.
'a'+'k'='ak'
'ak' put inside 'pinner' is 'pinnaker'.
's'+'pinnaker'='SPINNAKER'
(Other definitions for spinnaker that I've seen before include "Large racing sail" , "Lightweight sail" , "Type of sail" , "Large triangular sail at the front of a yacht" , "an expanse of cloth" .)