Turbulent period identified by firm in garden equipment plant (6-7)
I believe the answer is:
roller-coaster
'turbulent period' is the definition.
(turbulent period or event)
'firm in garden equipment plant' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'in' indicates putting letters inside.
'garden equipment' becomes 'roller' (as in a lawn roller).
'plant' becomes 'aster' (aster is a kind of plant).
'roller'+'aster'='rolleraster'
'co' going within 'rolleraster' is 'ROLLER-COASTER'.
'identified by' acts as a link.
(Another definition for roller-coaster that I've seen is " Fairground ride".)