smell a rat

lab rat

A student or employee who spends a great deal of time working in a laboratory.

poor as a rat

Synonym of poor as a church mouse.

rat run

A small, usually minor road used by a significant amount of traffic as a short cut or to avoid congestion on more major routes.

smell blood

To sense that one has an advantage over an adversary or rival.

smell fishy

To seem suspicious.

smell like a rose

To be regarded as appealing, virtuous, or respectable; to be untainted or unharmed.

smell like a tart's handbag

To smell strongly of perfume.

smell of an oily rag

A very small amount, or the absolute minimum (usually of money).