Sorry to bump this, I'm very behind with my listener crosswords and trying to catch up...
Anyway, this one I've finished, but was put wrong for quite a while by 16 down:
Steel bar Head of Engineering once put up to support giant water coolers (7)
...what is the word 'once' doing here? I assumed it was superfluous and had it, along with 'put', as one of my extra two-word phrases.