Yes -- You can give a hairball remedy.  Pet stores have several.  Has
it been checked by the Vet?  This is important to rule out trouble.
Does the crying start when she uses the litter pan?  Or -- could she
be asking for food.

<< Recently my four-year-old cat has started crying in the morning.  Not for
long, but enough to indicate that something is wrong.  This only happens in
the morning.  Is there such a thing as cats being constipated?  If so, is
there anything to be done? >>

You need to really look out and see if he/she isn't pooping.  If it's been much
more than a day or so, you should consult the vet. If it's a male cat, it can
also be crystals in his urethra.  

It is better to see the vet than worry.

Linda