Possible Clues:

• Cut back engineers' ditch
• Economise? Ditch entire play-centre first!
• Economise on part of army defensive system
• Shorten - taking middle sections with corers destroys twenty inches
• Tighten one's belt on kind of coat
• Dig it over again with a smaller staff
• Reduce, say expenditure or operations
• Introduce economies
• Cut back (on costs)
• Cut back sides of rare fish round river