DIY ledge on bookcase with rockers hard to lower (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

S H ELF (ledge on a bookcase) + ELP (Emerson, Lake & Palmer, English progressive rock supergroup formed in London in 1970; rockers) with H (hard, when describing pencil lead) being lowered to a place further down the entry to form SELF- H ELP