Ambushed by lunch as team's dissolute (8)
I believe the answer is:
unchaste
'dissolute' is the definition.
(I've seen this before)
'ambushed by lunch as team's' is the wordplay.
'ambushed by' indicates a hidden word (parts of the clue surround or 'ambush' the answer).
'UNCHASTE' is hidden within 'lunch as teams'.
(Other definitions for unchaste that I've seen before include "Dissolute" , "Immoral, wanton" , "Impure" , "Sexually immodest" , "Not decent and virtuous" .)