Optimism briefly at first in West Ham lifts players (7)
I believe the answer is:
oboists
'players' is the definition.
(oboist is a kind of player)
'optimism briefly at first in west ham lifts' is the wordplay.
I cannot really see how this works, but
'first' could be 'ist' (ist resembles 1st) and 'ist' is located in the answer.
The remaining letters 'obos' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for oboists that I've seen before include "Musicians" , "10 across group" , "Woodwind players" .)