Possible Clues:

• Random height substituted for length of square, requiring effort on the perimeter
• Slapdash, slipshod
• Chance
• Bloke caught out over venture that's hit-or-miss
• Careless, giving rise to expression of disgust over feature of golf course
• A measure of acidity shown by extreme characters in firm, so slipshod
• Random man's blown top with difficult to comprehend street map
• Careless fellow caught out by chance
• Random fellow's heading off: characters taking extreme positions in firm
• Casual hard cover for AP Herbert's first gazetteer?