Glaswegians, perhaps, hiding posh watches (6)
I believe the answer is:
scouts
'watches' is the definition.
('scout' can be a synonym of 'watch')
'glaswegians perhaps hiding posh' is the wordplay.
'glaswegians perhaps' becomes 'scots' (glaswegian is a kind of Scot).
'hiding' is an insertion indicator.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-u).
'scots' placed around 'u' is 'SCOUTS'.
(Other definitions for scouts that I've seen before include "They look out for talented people" , "Persons sent out to gather information - may be boys" , "Spotters" , "Lookouts or pathfinders" , "Young people's adventure organisation" .)