Firm blocking most of binoculars with warning regarding type of lens (9)

'regarding type of lens' is the definition.

'firm blocking most of binoculars with warning' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'blocking' indicates putting letters inside.
'most of' means to remove the last letter.
'binoculars' becomes 'bins' (short for binoculars).
'with warning' becomes 'cave' (I've seen this before. I am not sure about the 'with' bit.**).
'bins' with its last letter taken off is 'bin'.
'co' placed inside 'bin' is 'bicon'.
'bicon'+'cave'='BICONCAVE'