Doorstep millions holding stickers up (7)
I believe the answer is:
limpets
'stickers up' is the definition.
I can't tell whether this defines the answer.
'doorstep millions' is the wordplay.
'LIMPETS' is hidden back-to-front in amongst the letters.
However, I'm not sure how the hidden word is indicated.
'holding' is the link.
Can you help me to learn more?
(Other definitions for limpets that I've seen before include "'Molluscs, they cling to rocks (7)'" , "Proverbially clingy marine gastropods" , "Marine molluscs that cling tightly to rocks" .)