In AD&D 1e Player's Handbook, the Enlarge spell description specifically states:

It can be cast upon only a single creature or object.

It makes a differentiation between living and non-living matter:

The maximum volume of living material which can be initially affected is 10 cubic feet - for non-living matter, 5 cubic feet

Therefore, it's ambiguous as to what happens to a creature's clothing and armor (if it's wearing any) but it's implied that these don't grow which would imply the creature takes damage by instantly growing through a set of platemail, for instance. It is also not stated if the maximum space available is smaller than what size the creature or object will grow to. It is also left to the reader's imagination as to what happens if the reverse of the spell is cast and the creature shrinks and now is underneath a relatively heavy set of platemail, for instance.