1 - Rough-and-ready method by Tom's dictum? (4,2,5) - RULE OF THUMB
9 - They pull undergarments (7) - DRAWERS [DD]
10 - One boy back with another at the far end of ledge to remove covering (7) - {DIS<-}{ROB}{E}
11 - To a specified time peacekeepers get oil (5) - {UN}{TIL} TIL is Sesame but TIL by itself cannot mean OIL.
12 - PTA cheery about a perfect example (9) - ARCHETYPE*
13 - Give a dirty look to some of the bellowers (5) - LOWER [T]
15 - Shame! Dhonis veered off! Quarter of an hour lost! (9) - {DISHON*}{
18 - They keep shops smartened in a certain manner (9) - TRADESMEN*
21 - Company raised rejected rodent (5) - {COY}{PU<-}
22 - Young German gamely abandoned a broken playground equipment (6,3) - {JUNG}{LE GYM
24 - Caused injury by removing top with weapons (5) -
26 - Act with college head following ‘stop' order on a kind of research (7) - {POST*}{DO}{C}
27 - One who depletes to fall in the German case (7) - {D{RAIN}ER}
28 - His pic Colin morphed is inside the PC (7,4) - SILICON CHIP*
DOWN
1 - Communist to ponder over alien fish (3,6) - {RED} {MULL}{ET}
2 - Less than less (5) - LEAST [E]
3 - Bigger than big (9) - OVERLARGE [E]
4 - One who would wax eloquent over models, presumably (7) - TUSSAUD [CD]
5 - And the German, to sock pieces away, moves out (7) - {UND}{OCKS*}
6 - Criticise and wildly stab at one finally (5) - {BAST*}{E}
7 - Plump pudding (4-4) - ROLY-POLY [DD]
8 - First of samples, before it's withered (4) - {S}{ERE}
14 - By-no-means a strong vice (8) - WEAKNESS [CD]
16 - Canoeing — a sport for another time (4,5) - {ONCE {A}GAIN*}
17 - It brings you to where you began the journey (5,4) - ROUND TRIP [CD]
19 - Wonderful wise men raise a large amount (7) - {MAGI}{CAL<-}
20 - Itinerant, sane, leaders of Indian culture (7) - {NOMAD}{I}{C}
22 - Yes, in Germany, primarily puerile English quip (4) - {JA}{P}{E}
23 - Ditches fifty poems (5) - {L}{ODES}
25 - Insect hovers around Pole for a period (5) - {MO{N}TH}