Of course, you first want to do a change of variable $u = x/a$.
For positive integers $j$,
$$ \int_0^1 \frac{x^j\; dx}{\left(1-x^{3/4}\right)^{1/3}} = {\frac {4\;\Gamma \left( 4(j+1)/3 \right) \Gamma \left( 2/3
\right) }{3\;\Gamma \left( (4j+6)/3\right) }}
$$
Then $ \int_0^1 \frac{\cos(tx)\; dx}{(1-x^{3/4})^{1/3}}$ can be expressed
as a rather nasty combination of hypergeometric functions:
$$ \eqalign{\int_0^1 \frac{\cos(tx)\; dx}{(1-x^{3/4})^{1/3}} &=
{\frac {8\,\pi\,\sqrt {3}}{27}
{\mbox{$_6$F$_{11}$}\left({\frac{7}{24}},{\frac{5}{12}},{\frac{13}{24}},{\frac{19}{24}},{\frac{11}{12}},{\frac{25}{24}};\frac14,\frac13,\frac38,\frac12,\frac12,\frac58,\frac34,\frac56,{\frac{7}{8}},1,{\frac{9}{8}};\,{\frac {-{t}^{6}}{46656}}\right)}
}\cr
&- {\frac {81\,{t}^{2}}{220}
{\mbox{$_7$F$_{12}$}\left(\frac58,\frac34,{\frac{7}{8}},1,{\frac{9}{8}},\frac54,{\frac{11}{8}};\,{\frac{7}{12}},\frac23,{\frac{17}{24}},\frac56,\frac56,{\frac{23}{24}},{\frac{13}{12}},\frac76,{\frac{29}{24}},\frac43,\frac43,{\frac{35}{24}};\,{\frac {-{t}^{6}}{46656}}\right)}
}\cr
&+{\frac {187\,\sqrt {3} \Gamma \left( \frac23 \right)^{3}{
t}^{4}}{11856\,\pi}
{\mbox{$_6$F$_{11}$}\left({\frac{23}{24}},{\frac{13}{12}},{\frac{29}{24}},{\frac{35}{24}},{\frac{19}{12}},{\frac{41}{24}};\,{\frac{11}{12}},{\frac{25}{24}},\frac76,\frac76,{\frac{31}{24}},{\frac{17}{12}},\frac32,{\frac{37}{24}},\frac53,\frac53,{\frac{43}{24}};\,{\frac {-{t}^{6}}{46656}}\right)}
}
}$$
I don't know if this can be simplified.