It comes from the following sentence which is spoken by a boy who normally uses Tokyo dialect.
おれもだあ! おれもヘッドギャなんてちゃらくさいもんはいらんっ グローブも体重に関係なくいちばんでっかい十二オンスだ
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Most likely it is ちゃらい＋くさい, meaning 'really gaudy/cheap' or 'reeking of gaudiness'.
When used as a suffix, ～くさい usually adds a negative connotation to whatever precedes it. This can be used in the literal sense when there is an actual perceptible odour (酒臭い, 汗くさい), or in the figurative sense to mean 'evoking a sense of ...' (嘘くさい, 邪魔くさい).
In your example, it would be a figurative use of チャラい. However, it appears to be a somewhat irregular usage. As a suffix, ～くさい usually attaches directly to nouns or na-adjectives rather than i-adjectives. So dropping the い of チャラい could be considered a kind of slang usage, perhaps.
It would be interesting to find other examples of i-adjective stem + くさい. I have a vague memory of hearing えらくさい（偉い+くさい) somewhere but I can't be sure.