Do not use list as variable name. You can take a look at the following code too:
clist = ['element1\t0238.94', 'element2\t2.3904', 'element3\t0139847', 'element5']
clist = [x[:x.index('\t')] if '\t' in x else x for x in clist]
Or in-place editing:
for i,x in enumerate(clist):
if '\t' in x:
clist[i] = x[:x.index('\t')]