ThereAbouts has it right. However as a straightforward equity...

ThereAbouts has it right.
However as a straightforward equity instrument, it certainly is not defensive in the larger context. This shows the drawdowns of the investment over time i.e. negative months. Green shading is VHY with a peak drawdown of -20% early this year. By comparison, the ASX300 (shown as the purple dotted line), had a peak drawdown of 13.5% at the same time.

This highlights the issues to understand with a vehicle like VHY. It's an 'Alternative Beta' or 'Smart Beta' ETF which uses a rules based index rather than a market cap weight like the ASX300. You need to understand the rules of the index construction to get an appreciation of how it will act in different scenarios. In VHY's case, it's exceedingly simplistic and highly exposed to the risk of loading up on stocks that are due for a correction (i.e. financials and miners in this case). If you are looking for a yield ETF, it's not my first choice. Personally I believe RDV is a better bet as its rules better take into account dividend sustainability. VHY will shoot the lights out in good times, but get a pounding when things turn sour.