Good uniform one found tossed in vermin-infested tip (8)
I believe the answer is:
gratuity
'tip' is the definition.
(I know that tip can be written as Gratuity)
'good uniform one found tossed in vermin-infested' is the wordplay.
'good' becomes 'g' (abbreviation).
'uniform' becomes 'U' (phonetic alphabet: alpha, bravo, charlie etc.).
'one' becomes 'I' (Roman numeral).
'found tossed in' means one lot of letters goes inside another.
'vermin-infested' becomes 'ratty' (infested with rats).
'u'+'i'='ui'
'ui' put inside 'ratty' is 'ratuity'.
'g'+'ratuity'='GRATUITY'
(Other definitions for gratuity that I've seen before include "Tip (to waiter)" , "present" .)