He plans to 'thin' (out) the young carrots in the garden. [=to remove some of them so that there is more room between the remaining carrots]
His hair is a little 'thin' on top. = He's a little 'thin' on top. [=he does not have a lot of hair on the top of his head]
The bank's decision to raise rates could be 'the thin end of the wedge'. [=many other banks may also decide to raise rates]
(..) There's no need for you to go yourself, Frank. Get rid of the fucking tail! All right. Fucking rats. It's wearing me thin. Francis, it's a nation of fucking rats. Stop, stop. Pull them off Costello. There's no need to surveil him. - What are you saying? - I got it from an undercover. (..)2006 The Departed