Solution to 4D has been deliberately left unsolved and is to be answered only by a non-regular / novice commenter, with proper annotation. Those who have answered earlier in the week, please give others a chance.
ACROSS
1 Device that’s arresting the curling (12) STRAIGHTENER* &lit
10 Having wine before light show (7) PORTRAY {PORT}{RAY}
11 Relative, after losing heart, has broken free (7) UNLEASH {UNcLE}{HAS*}
12 Team frequently dealt with No. 2! (6) ELEVEN {dEaLt}{EVEN}
15 Get old men to build a place to stay (9) LODGEMENT*
16 Should be 0 - N (5) OUGHT nOUGHT
17 Permitted in felicitations (5) LICIT [T]
22 The gutted North American town shows resolve (8) TENACITY {ThE}{NA}{CITY}
24 Detector said to be cut (6) CENSOR (~senser)
26 Go from a Mediterranean Island (7) EXCRETE {EX}{CRETE}
27 Say, grow old and mean (7) AVERAGE {AVER}{AGE}
28 Having been around for a while, it’s horrible — landing’s not good (4-8) LONG-STANDING {LANDINGS+NOT+G}*
DOWN
2 Plant poorly watered (7) TARWEED*
4 Men in fashion, say (4) G?Y? (Addendum - GUYS (~guise) - See comments)
5 Standard type of telephone around South (10) TOUCHSTONE {TOUCH}{S}{TONE} (Correction {TOUCH{S}TONE) - See comments)
6 Many Londoners wearing this material (5) NYLON [T]
7 Motorist runs over a dog outside hospital (4,3) ROAD HOG {R}{O}{A}{D{H}OG}
14 Joint strain for sewer (10) SEAMSTRESS {SEAM}{STRESS}
16 Bad month — need improving (2,3,4) ON THE MEND*
17 Message left by Vulcan after commencement (6) LETTER {L}{sETTER}
18 Conservative leader in lacy clothes? Looking back, it’s ironic (7) CYNICAL {Co...e}{Y{NI}CAL<=}
20 Soil surrounding us giving support (7) SUSTAIN {S{US}TAIN}
21 Old marathoner finally entered and ran (6) DARTED {DA{m...eR}TED}
23 Fresh, cold and low in fat (5) CLEAN {C}{LEAN}
25 Jabber about a story (4) SAGA {GAS<=}{A}
Reference List
Island = I, Good = G, South = S, Runs = R, Over = O, Hospital = H, Left = L, Cold = C