Yes, just dig out about an 10-12 circle of sod around the head, remove the head and straighten it out. It could just be that the fitting is twisted and needs to be twisted back (along with tightening the clamp). Depending on your installation, it could be a funny/flex pipe and if that's the case you may have to dig it back just slightly so you can turn it and make sure it stays that way.

I had this problem too, and decided to try and 'anchor' the heads into place a bit more securely using some ABS couplings. It's worked pretty well so far. The harder the soil -- especially clay, ugh -- the better the anchoring effect, I bet.

You can see the top edge of the ABS collar peeking up above the turf, above. See my step-by-step install here: http://havingfunalongtheway.com/save-the-drowning-sprinkler-heads/