As wide as the Clyde

The Clyde refers to a river in south Scotland that flows northwest.
The term ‘as wide as the Clyde’ likely denotes the length or size of the object or idea referred to (i.e. it can refer to figurative or actual lengths and distances).

Alison Thewliss (SNP frontbencher)
...the NAO report blows a hole ‘as wide as the Clyde’ through everything the Tories have been saying on Universal Credit.