Group excursion almost over (4)
I believe the answer is:
trio
'group' is the definition.
(a group of three)
'excursion almost over' is the wordplay.
'excursion' becomes 'trip' (I've seen this before).
'almost' means to remove the last letter (most of the word but not all of it).
'over' becomes 'o' (cricket abbreviation).
'trip' with its final letter removed is 'tri'.
'tri'+'o'='TRIO'
(Other definitions for trio that I've seen before include "(Composition for) three performers" , "Ensemble musical piece, eg Beethoven's 'Archduke'" , "Three of a kind" , "Bee Gees, Supremes or Andrews Sisters, say" , "Beethoven's 'Archduke', for example" .)