Crossword Genius

Advance slowly under His roof? (4)

Ross

I believe the answer is:

inch

I'm a little stuck... Click here to teach me more about this clue!

This might be a double definition.

'advance slowly' is the first definition.
(I've seen this before)

'under his roof?' is the second definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

Can you help me to learn more?

(Other definitions for inch that I've seen before include "Move in tiny increments" , "make slow progress" , "Rare bird follower" , "Creep, edge" , "Move along gradually" .)

I've seen this clue in The Telegraph and The Sun.
Want a hint initially instead of a full solution? Install my app